Introduction to Radiation Detection

A Presentation for Science Saturday

Alex EndersDeputy Program Manager,

Second Line of Defense SupportOak Ridge National Laboratory

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What Is Radiation?

ALPHA

BETA

GAMMA

NEUTRON

P A P E R

A L U M I NU M

L E A D

W A T E R

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What Is Gamma Radiation?

Radio

Microwaves

Visible

X-Ray

Gamma Ray

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Radiation Is All Around Us

http://web.mit.edu/newsoffice/1994/safe-0105.html

Astronauts:25,000 millirem / mission !

Average Person Living in the US:

620 millirem per year

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What Is Radiation Detection?

Photon

Magic!!

Electrons

Happy Engineer

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The “Magic” of Geiger-Muller Tubes

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A Peek Inside a G-M tube

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Lots of Other Types of Gamma Radiation Detectors, too

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Find the Hidden Radioactive Material

• Different models will be set up with hidden radioactive material

• Use the radiation detector to determine where the hidden material is located

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Video

Courtesy of the Weather Channel:http://www.weather.com/video/web-extra-measuring-gamma-rays-34355

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Basic electricity concepts

• The relation between current, voltage and resistance in an electric circuit is described by Ohm’s Law– I = V/R – “current equals voltage divided by resistance”– current (amps) is a measure of the flow of electrons– voltage (volts) is the force that makes the electrons move– resistance (ohms) are forces that oppose the flow

• Think of a water hose– current is how much water goes through– voltage is the water pressure– resistance is the size of the pipe– If the pressure is high (high voltage), more water comes out– If the pipe is small (high resistance) less water will come out

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How to use breadboards

• Breadboards help you build electronic circuits without soldering components together.

• A breadboard is an array of conductive strips with holes where component leads can be inserted.

• The links in the following figures are connected electrically.

• The circuit is made when components are connected by inserting them into breadboard rows that are electrically the same.

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Breadboards(which pins are connected to each other)

http://www.instructables.com/id/How-to-use-a-breadboard/?ALLSTEPS

The power voltage is the red line on the left, whereas the ground is the blue line on the right.

The bread board is connected as shown below.

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Components of your circuit

• Photoresistor made of cadmium sulfide (CdS)

• Resistance with no light is 1 MΩ

• Resistance decreases when light shines on the CdS, down to 8000 Ω

• Resistance changes by a factor of 125

• Battery pack consists of 3 AAA batteries in series

• Each has an output voltage of 1.5 V

• Total voltage is 4.5 V (3 x 1.5)

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Components of your circuit (contd.)

• This button is only “ON” while it is activated (i.e. momentary button)

• The leads directly across from each other are always connected

• The leads beside each other are only connected when the button is pressed

• LED (light emitting diode)

• available in many colors

• They only work when the electrons flow the right direction

• The longer lead must be connected to the positive terminal of the battery

• these LEDs have a current limit of 20 mA

always connected

only connected while button is pressed

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Electrical Schematic and picture of setup

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How much current is flowing in your circuit?

• I = V/R

• Voltage is supplied by 3 AAA batteries with 1.5 V each

• Resistance of the CdS photoresistor– 1 MΩ in the dark– 8000 Ω (minimum) when light shines on it

• (5 mA)

• (600 mA)