NUCLEAR PHYSICS

Composition of MatterAll of matter is composed of at least three fundamental particles (approximations)

All of matter is composed of at least three fundamental particles (approximations)

Electron Electron ee-- 911 x 10 911 x 10-31-31 kg kg -16 x 10 -16 x 10-19 -19 C C

Proton Proton pp 1673 x 101673 x 10-27-27 kg +16 x 10 kg +16 x 10-19 -19 C 3 fmC 3 fm

Neutron Neutron nn 1675 x 101675 x 10-31-31 kg kg 0 0 3fm 3fm

DefinitionsA nucleon is a general term to denote a nuclear particle - that is either a proton or a neutron

The atomic number Z of an element is equal to the number of protons in the nucleus of that element

The mass number A of an element is equal to the total number of nucleons (protons + neutrons)

Nuclear Size

The shape of the nucleus is taken spherical because for a given volume this shape possesses the least surface area

The nuclear density remains approximately constant over most of the nuclear volume This means that the nuclear volume is proportional to the number of nucleons ie mass number A

Hence radius of nucleus R 31

A

31

ARR o

where is a constant having value 148 x 10-15 m oR

Atomic Mass Unit uOne atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12

Atomic mass unit 1 u = 16606 x 10-27 kg

Common atomic masses

Proton 1007276 u Neutron 1008665 u

Electron 000055 u Hydrogen 1007825 u

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Composition of MatterAll of matter is composed of at least three fundamental particles (approximations)

All of matter is composed of at least three fundamental particles (approximations)

Electron Electron ee-- 911 x 10 911 x 10-31-31 kg kg -16 x 10 -16 x 10-19 -19 C C

Proton Proton pp 1673 x 101673 x 10-27-27 kg +16 x 10 kg +16 x 10-19 -19 C 3 fmC 3 fm

Neutron Neutron nn 1675 x 101675 x 10-31-31 kg kg 0 0 3fm 3fm

DefinitionsA nucleon is a general term to denote a nuclear particle - that is either a proton or a neutron

The atomic number Z of an element is equal to the number of protons in the nucleus of that element

The mass number A of an element is equal to the total number of nucleons (protons + neutrons)

Nuclear Size

The shape of the nucleus is taken spherical because for a given volume this shape possesses the least surface area

The nuclear density remains approximately constant over most of the nuclear volume This means that the nuclear volume is proportional to the number of nucleons ie mass number A

Hence radius of nucleus R 31

A

31

ARR o

where is a constant having value 148 x 10-15 m oR

Atomic Mass Unit uOne atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12

Atomic mass unit 1 u = 16606 x 10-27 kg

Common atomic masses

Proton 1007276 u Neutron 1008665 u

Electron 000055 u Hydrogen 1007825 u

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

DefinitionsA nucleon is a general term to denote a nuclear particle - that is either a proton or a neutron

The atomic number Z of an element is equal to the number of protons in the nucleus of that element

The mass number A of an element is equal to the total number of nucleons (protons + neutrons)

Nuclear Size

The shape of the nucleus is taken spherical because for a given volume this shape possesses the least surface area

The nuclear density remains approximately constant over most of the nuclear volume This means that the nuclear volume is proportional to the number of nucleons ie mass number A

Hence radius of nucleus R 31

A

31

ARR o

where is a constant having value 148 x 10-15 m oR

Atomic Mass Unit uOne atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12

Atomic mass unit 1 u = 16606 x 10-27 kg

Common atomic masses

Proton 1007276 u Neutron 1008665 u

Electron 000055 u Hydrogen 1007825 u

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Size

The shape of the nucleus is taken spherical because for a given volume this shape possesses the least surface area

The nuclear density remains approximately constant over most of the nuclear volume This means that the nuclear volume is proportional to the number of nucleons ie mass number A

Hence radius of nucleus R 31

A

31

ARR o

where is a constant having value 148 x 10-15 m oR

Atomic Mass Unit uOne atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12

Atomic mass unit 1 u = 16606 x 10-27 kg

Common atomic masses

Proton 1007276 u Neutron 1008665 u

Electron 000055 u Hydrogen 1007825 u

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Atomic Mass Unit uOne atomic mass unit (1 u) is equal to one-twelfth of the mass of the most abundant form of the carbon atom--carbon-12

Atomic mass unit 1 u = 16606 x 10-27 kg

Common atomic masses

Proton 1007276 u Neutron 1008665 u

Electron 000055 u Hydrogen 1007825 u

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

2 8 3 x 10 msE mc c 2 8 3 x 10 msE mc c

Mass and Energy Einsteinrsquos equivalency formula for m and E

The energy of a mass of 1 u can be found

E = (1 u)c2 = (166 x 10-27 kg)(3 x 108 ms)2

E = 149 x 10-10 J OrOr E = 9315 MeV

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

The Mass Defect

The mass defect is the difference between the rest mass of a nucleus and the sum of the rest masses of its constituent nucleons A

Binding Energy

The binding energy of a nucleus is the energy required to separate a nucleus into its constituent parts

EB = mDc2 where mD is the mass defect

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Binding Energy Vs Mass Number

Mass number ABin

ding

Ene

rgy

per

nucl

eon

50 100 150 250200

2

6

8

4

Curve shows that EB increases with A and peaks at A = 60 Heavier nuclei are less stable

Green region is for most stable atoms

For heavier nuclei energy is released when they break up (fission) For lighter nuclei energy is released when they fuse together (fusion)

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Radioactivity

bull The phenomenon of spontaneous emission of radiations (αβ and γ radiations) from a substance (generally elements having their atomic number higher than 82 in the periodic table)

bull Discovered by Henry Bacquerel in 1896bull Properties of αβ and γ radiations-

Composition Ionization Power Penetration power Effect on photographic plate

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Laws of Radioactive disintegrations-

1- The Radioactive disintegrations happens due to the emission of α β and γ radiations

2- The natural disintegration is totally statistical ie which atom will disintegrate first is only a matter of chance

3- The number of atoms which disintegrate per second is proportional to the number remaining atoms present at any instant ie-

-dNdt α N or -dNdt = λN

(where λ is a constant of proportionality and is known as the decay constant)

or N = N0e-λt

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Half Life Period (T)-

bull The time in which half of the radioactive substance gets disintegrates is known as half life of that material

T = 0693λ

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

General Properties of Nucleusmdash

1- Nuclear mass= Mass of all Neutrons + Mass of all protonsmp= 167261 x 10-27 Kg = 1007277 amu mn= 167492 x 10-27 Kg = 1008666 a m u

2- Nuclear Charge- Total charge due to the protons

3- Nuclear radius- Nuclear radius is measured by the measurement of the directions of scattered protons neutrons electrons

R = R0A13

Where R0 is a constant with value = 14 x 10-15 MeterA = Mass Number of the element

4- Nuclear density= Nuclear Mass [43( π R3)]

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

The Mass Difference and Nuclear Binding Energy-

bull The mass of the nucleus is always less than the sum of masses of its constituents

bull The difference in measured mass (M in a m u) and mass number (A) is called mass defect (∆M)

bull The Binding energy of the nucleus (E) = ∆M (in amu) x (931 MeV)

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Forces

bull A nucleus contains positively charged protons and uncharged neutrons

bull A repulsive force works between protons inside the nucleus

bull Nuclear forces overcome with these repulsive forces to give a stable nucleus

bull Neutrons and protons can be converted in to each other by the exchange of a new particle meson

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Meson theory of Nuclear Forces by Yukawa (1935)

bull A meson may be π+ π- or π0

A neutron by accepting a π+ meson converted in to a proton

A proton by ejecting a π+ meson converted in to a neutron

bull A neutron by ejecting a π- meson converted in to a proton

bull A proton by accepting a π- meson converted in to a neutron

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

bull Two neutron can exchange π0 mesons which result in the exchange forces between them

bull This exchange of meson is responsible for the generation of exchange forces which is responsible for the stability of nucleus

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Fission

bull The phenomenon of breaking of heavy nuclie in to two or more light nuclei of almost same masses is known as the nuclear fission

bull Discovered by Otto Hahn and Strassman (Germans) in 1939

bull In nuclear fission large amount of energy is liberated

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

bull Theory of Nuclear Fission- Liquid Drop Model-bull By Bohr and Wheelerbull The nucleus is assumed to be similar to a drop of the liquidbull Nucleus remains in balance due to the exchangeforces and the

repulsive forces between its constituentsbull Due to this balance nucleus remains in spherical sizebull When this balance is disturbed by the incident neutrons the

spherical shape is distortedbull The surface tension force tend to recover the spherical size so drop

attains a dumb-bell shapebull Due to disbalance in the exchange and coulombic forces the dumb-

bell breaks in two spherical parts (ie two separate nuclie)

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

bull Nuclear fusion is the formation of a heavier nucleus by fusing of two light nuclei

bull In this process mass of the resulting nucleus is less than the masses of constituent therefore according to Einsteinrsquos mass energy equivalence enormous amount of energy is released

bull Fusion reactions take place at very high temperature

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

U23892

Gamma ray

Th234

90

He4

2

Spontaneous Fission

Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into 2 smaller nuclei

Energy is being released as a result of the fission reaction

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Induced Fission

Nuclear fission can be induced by bombarding atoms with neutrons resulting in the splitting of nuclei into two smaller nuclei

Induced fission decays are also accompanied by the release of neutrons

nKrBanU 10

9236

14156

10

23592 3

Energy is being released as a result of the fission reaction

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Fusion

In nuclear fusion two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number

EnergynHeHH 10

42

31

21

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Hydrogen (proton) fusion

p+

p+

Like electrical charges repel So protons in a gas avoid `collisionsrsquo

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Hydrogen (proton) fusion

p+

p+

However as a gas temperature goes up the average speed of the particles goes up and the protons get closer before repelling one another If the proton get very close the short-range nuclear force fuses them together

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Antimatter When two protons fuse almost immediately one turns into a

neutron by emitting a positively charged electron (known as a positron) The e+ is antimatter When it comes into contact with its matter partner (e-) it annihilates entirely into energy

NeutrinoThis is a chargeless perhaps massless particle which has a tiny crossection for interaction with other types of matter The mean free path in lead is five light years

Neutrinos were first postulated in 1932 to account for missing angular momentum and energy in beta-decay reactions (when a proton becomes a neutron and emits a positron)

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Force

The nuclear force is the force between two or more nucleons It is responsible for binding of protons and neutrons into atomic nuclei

The force is powerfully attractive between nucleons at distances of about 1 femtometer (fm) between their centers but rapidly decreases to insignificance at distances beyond about 25 fm

At very short distances less than 07 fm it becomes repulsive and is responsible for the physical size of nuclei since the nucleons can come no closer than the force allows

At short distances (less than 17 fm or so) the nuclear force is stronger than the Coulomb force between protons it thus overcomes the repulsion of protons inside the nucleus

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Proton-Proton Cycle

109years 1 sec

He3

H1

He4

Gamma ray

106year

H1

H1

H1

H1

H1

H1

H1

neutron neutrino

positron

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Proton-Proton Cycle

bull The net result is

4H1 --gt He4 + energy + 2 neutrinos

where the released energy is in the form of gamma rays

Each cycle releases ~25 MeV

For the proton-proton cycle the gas temperature needs to be gt107K

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

CNO cycle

Energy released ~2672 MeV per cycle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Source of Energy of Stars

bull The source of energy of stars is Fusion reactionbull Our sun shares the ldquoProton-Proton Fusion Cyclerdquo

with the smallest known starsbull Larger stars known to ldquoburnrdquo with different cycles

such as the ldquocarbon cyclerdquo

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Nuclear Radiation Measurements All the methods for detection of radioactivity are based on

interactions of the charged particles because interaction results in the production of ions and release of energy

Detectors are used to detect and record the number of particles emitted in various experiments involved in the study of nuclear radiation disintegration and transmutation

Detectors

Based on Ion collection method

Based on Light emission method

Example Proportional Counter GM Counter

Example Scintillation Counter

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Types of detectors

ndash Gas-filled detectors consist of a volume of gas between two electrodes

ndash In scintillation detectors the interaction of ionizing radiation produces UV andor visible light

ndash Semiconductor detectors are especially pure crystals of silicon germanium or other materials to which small amounts of I mpurity atoms have been added so that they act as diodes

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Types of detectors (cont)

bull Detectors may also be classified by the type of information producedndash Counters indicate the number of interactions

occurring in the detector ndash Spectrometers yield information about the energy

distribution of the incident radiationndash Dosimeters indicate the net amount of energy

deposited in the detector by multiple interactions

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Modes of operation

bull In pulse mode the signal from each interaction is processed individually

bull In current mode the electrical signals from individual interactions are averaged together forming a net current signal

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Dead time

bull The minimum time taken by a radiation detector in between two successive detections

bull GM counters have dead times ranging from tens to hundreds of microseconds most other systems have dead times of less than a few microseconds

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Detection efficiency

bull The efficiency (sensitivity) of a detector is a measure of its ability to detect radiation

bull Efficiency of a detection system is defined as the probability that a particle or photon emitted by a source will be detected

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

efficiency Intrinsic efficiency Geometric Efficiency

detector reachingNumber

detectedNumber

emittedNumber

detector reachingNumber Efficiency

emittedNumber

detectedNumber Efficiency

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Gas-filled detectors

bull A gas-filled detector consists of a volume of gas between two electrodes with an electrical potential difference (voltage) applied between the electrodes

bull Ionizing radiation produces ion pairs in the gasbull Positive ions (cations) attracted to negative

electrode (cathode) electrons or anions attracted to positive electrode (anode)

bull In most detectors cathode is the wall of the container that holds the gas and anode is a wire inside the container

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Schematic diagram of a Gas Filled Detector

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Types of gas-filled detectors

bull Three types of gas-filled detectors in common usendash Ionization chambersndash Proportional countersndash Geiger-Mueller (GM) counters

bull Type determined primarily by the voltage applied between the two electrodes

bull Ionization chambers have wider range of physical shape (parallel plates concentric cylinders etc)

bull Proportional counters and GM counters must have thin wire anode

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

GM counters Main Features

bull GM counters used for the detection of αβγ rays protons etc

bull Gas amplification produces billions of ion pairs after an interaction

bull The only difference with a Proportional Counter is of operating voltage

bull Operating voltage is 800-2000 Voltsbull Works on pulse mode

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Gas Multiplication

ndash+

ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash

+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+ndash+

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

CONSTRUCTION-A Metallic tube with thin wire (anode) in center wall of the tube works as cathodeTube is usually filled with noble gas (eg argon) at low pressure with some additives as quenchers eg carbon dioxide methane isobutane)-Charged particle in gas ionization electrons liberatedrArr rArr-Electrons accelerated in electric field liberate other electrons by rArrionization which in turn are accelerated and ionize rArr ldquoavalanche of electronsrdquo-Quenching is the process of terminating the discharge after each detection- The time taken for this is known as dead time of the counter

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

PULSE

Cathode

ANODE

Pulse Counter

Mixture of Argon and ethyl alcohol

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Geiger-Muller Counter

Vacuum tube amplifier

α - particle

Geiger-Muller Counter

The efficiency of the counter is defined as the ratio of the observed countssec to the number of ionizing particles entering the counter per second

Counting efficiency is its ability of counting if at least one ion-pair is produced in it

slpe1

Where s = specific ionization at one atmosphere p = pressure in atmosphere l = path length of the ionization particle in the counter

Proportional Counter

Proportional Counter

Proportional Counters1048708 similar in construction to Geiger-Muumlller counter but works in different HV regime (200- 800 Volts)1048708 metallic tube with thin wire in center filled with gas HV between wall (- ldquocathoderdquo) and central wire (+rdquoanoderdquo) strong electric field near wirerArr1048708 gas is usually noble gas (eg argon) with some additives eg carbon dioxide methane isobutane) as ldquoquenchersrdquo1048708Radiation detected - αβγ rays

Scintillation Counter

Phosphor Photomultiplier tube

Amplifier scaler and register

Incident Radiation

Light Pulse

Electric Pulse

Scintillation detectors

bull Scintillators are used in conventional film-screen radiography many digital radiographic receptors fluoroscopy scintillation cameras most CT scanners and PET scanners

bull Scintillation detectors consist of a scintillator and a device such as a PMT that converts the light into an electrical signal

Scintillators

bull Desirable propertiesndash High conversion efficiencyndash Decay times of excited states should be shortndash Material transparent to its own emissionsndash Color of emitted light should match spectral sensitivity

of the light receptorndash For x-ray and gamma-ray detectors should be large

ndash high detection efficienciesndash Rugged unaffected by moisture and inexpensive to

manufacture

Scintillators (cont)

bull Amount of light emitted after an interaction increases with energy deposited by the interaction

bull May be operated in pulse mode as spectrometers

bull High conversion efficiency produces superior energy resolution

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Scintillation Counter

Phosphor Photomultiplier tube

Amplifier scaler and register

Incident Radiation

Light Pulse

Electric Pulse

Scintillation detectors

bull Scintillators are used in conventional film-screen radiography many digital radiographic receptors fluoroscopy scintillation cameras most CT scanners and PET scanners

bull Scintillation detectors consist of a scintillator and a device such as a PMT that converts the light into an electrical signal

Scintillators

bull Desirable propertiesndash High conversion efficiencyndash Decay times of excited states should be shortndash Material transparent to its own emissionsndash Color of emitted light should match spectral sensitivity

of the light receptorndash For x-ray and gamma-ray detectors should be large

ndash high detection efficienciesndash Rugged unaffected by moisture and inexpensive to

manufacture

Scintillators (cont)

bull Amount of light emitted after an interaction increases with energy deposited by the interaction

bull May be operated in pulse mode as spectrometers

bull High conversion efficiency produces superior energy resolution

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Scintillation detectors

bull Scintillators are used in conventional film-screen radiography many digital radiographic receptors fluoroscopy scintillation cameras most CT scanners and PET scanners

bull Scintillation detectors consist of a scintillator and a device such as a PMT that converts the light into an electrical signal

Scintillators

bull Desirable propertiesndash High conversion efficiencyndash Decay times of excited states should be shortndash Material transparent to its own emissionsndash Color of emitted light should match spectral sensitivity

of the light receptorndash For x-ray and gamma-ray detectors should be large

ndash high detection efficienciesndash Rugged unaffected by moisture and inexpensive to

manufacture

Scintillators (cont)

bull Amount of light emitted after an interaction increases with energy deposited by the interaction

bull May be operated in pulse mode as spectrometers

bull High conversion efficiency produces superior energy resolution

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Scintillators

bull Desirable propertiesndash High conversion efficiencyndash Decay times of excited states should be shortndash Material transparent to its own emissionsndash Color of emitted light should match spectral sensitivity

of the light receptorndash For x-ray and gamma-ray detectors should be large

ndash high detection efficienciesndash Rugged unaffected by moisture and inexpensive to

manufacture

Scintillators (cont)

bull Amount of light emitted after an interaction increases with energy deposited by the interaction

bull May be operated in pulse mode as spectrometers

bull High conversion efficiency produces superior energy resolution

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Scintillators (cont)

bull Amount of light emitted after an interaction increases with energy deposited by the interaction

bull May be operated in pulse mode as spectrometers

bull High conversion efficiency produces superior energy resolution

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Materials

bull Sodium iodide activated with thallium [NaI(Tl)] coupled to PMTs and operated in pulse mode is used for most nuclear medicine applicationsndash Fragile and hygroscopic

bull Bismuth germanate (BGO) is coupled to PMTs and used in pulse mode as detectors in most PET scanners

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Photomultiplier tubes

bull PMTs perform two functionsndash Conversion of ultraviolet and visible light

photons into an electrical signalndash Signal amplification on the order of millions to

billions

bull Consists of an evacuated glass tube containing a photocathode typically 10 to 12 electrodes called dynodes and an anode

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Dynodes

bull Electrons emitted by the photocathode are attracted to the first dynode and are accelerated to kinetic energies equal to the potential difference between the photocathode and the first dynode

bull When these electrons strike the first dynode about 5 electrons are ejected from the dynode for each electron hitting it

bull These electrons are attracted to the second dynode and so on finally reaching the anode

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

eta minus-) decayexample 6C14

7N14 + -10 + 00

A neutron turned into a proton by emitting an electron however one particle [the neutron] turned into two [the proton and the electron]

Charge and mass numbers are conserved but since all three (neutron proton and electron) are fermions [spin 12 particles] angular momentum particle number and energy are not Need the anti-neutrino [0] to balance everything

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay

Positron (+) decayexample 6C11

5B11 + +10 + 00

A proton turns into a neutron by emitting a positron however one particle [the proton] turned into two [the neutron and the positron]

Charge and mass numbers are conserved but since all three are fermions [spin 12 particles] angular momentum particle number and energy are not Need the neutrino [0] to balance everything

• NUCLEAR PHYSICS
• Composition of Matter
• Definitions
• Nuclear Size
• Atomic Mass Unit u
• Mass and Energy
• The Mass Defect
• Binding Energy Vs Mass Number
• Radioactivity
• Laws of Radioactive disintegrations-
• Half Life Period (T)-
• General Properties of Nucleusmdash
• The Mass Difference and Nuclear Binding Energy-
• Nuclear Forces
• Meson theory of Nuclear Forces by Yukawa (1935)
• Slide 16
• Nuclear Fission
• Slide 18
• Slide 19
• Slide 20
• Spontaneous Fission
• Slide 22
• Nuclear Fusion
• Hydrogen (proton) fusion
• Slide 25
• Antimatter
• Nuclear Force
• Proton-Proton Cycle
• Slide 29
• Slide 30
• Source of Energy of Stars
• Nuclear Radiation Measurements
• Types of detectors
• Types of detectors (cont)
• Modes of operation
• Dead time
• Detection efficiency
• Slide 38
• Gas-filled detectors
• Slide 40
• Types of gas-filled detectors
• GM counters Main Features
• Slide 43
• Slide 44
• Slide 45
• Geiger-Muller Counter
• Slide 47
• Proportional Counter
• Slide 49
• Scintillation Counter
• Scintillation detectors
• Scintillators
• Scintillators (cont)
• Materials
• Photomultiplier tubes
• Slide 56
• Dynodes
• Beta minus (b-) decay
• Positron (b+) decay