TIME 0F FLIGHT (TOF) METHOD IN TIME 0F FLIGHT (TOF) METHOD IN SANS TECHNIQUESANS TECHNIQUE

MBULE P.SMBULE P.S11,MALINDISA C,MALINDISA C22, KOAO L.F, KOAO L.F11 Supervisor : Dr. KUKLIN A.LSupervisor : Dr. KUKLIN A.L33

1.1.UNIVERSITY OF THE FREESTATEUNIVERSITY OF THE FREESTATE2.2.UNIVERSITY OF ZULULANDUNIVERSITY OF ZULULAND

3.3.JOINT INSTITUTE OF NUCLEAR RESEARCHJOINT INSTITUTE OF NUCLEAR RESEARCHDUBNA, RUSSIADUBNA, RUSSIA

September September

South African Student Summer Practice 2009South African Student Summer Practice 2009

Laboratory WorkLaboratory Work

OUTLINEOUTLINE

IntroductionWhat is SANSNeutrons sourcesSANS EquipmentSANS ApplicationsAcknowledgement

IntroductionIntroduction

• Time of flight (TOF)- Method used to measure the time that it takes for a particle, an object or stream to reach a detector while travelling over a known distance.

• Small angle neutron scattering- Is a laboratory technique where radiation is elastically scattered by the sample and the resulting scattering pattern is analysed to provide information about the size, shape and the orientation of some components of the sample.

Why use neutrons?Why use neutrons?• Neutrons scatter from materials by

interacting with the nucleus of an atom rather than the electron cloud.

• The neutrons have a high penetrating probe• Neutrons have wavelengths similar to

spacings, permitting diffraction measurements to be performed.

Sources of neutrons.Sources of neutrons.• Nuclear Reactor A device in which

nuclear chain reaction are initiated, controlled and sustained at a steady rate

A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, leading to a self propagating number of these reactions.

Fig 1: Possible nuclear fission chain reaction

•Spallation neutron source

•When a fast particle such as high-energy proton bombards a heavy atomic nucleus, neutrons are “spalled” in a nuclear reaction called spallation.

•For every proton striking the nucleus, 20 to 30 neutrons are expelled.

Fig 2: Schematic illustration of Spallation

Small angle neutron scattering Small angle neutron scattering YuMO spectrometerYuMO spectrometer

1 -- reflectors, 2 -- active zone with moderator, 3 -- breaker (shutter), 4 -- changeable collimator with different beam-holes, 5 -- vacuum tube, 6 -- adjustable collimator determining the size and position of the direct beam, 7 -- thermostats, 8 -- sample container, 9 -- sample table, 10 -- standard vanadium scatterer, 11, 12 -- ``old'' and ``new'' detectors, 13 -- direct beam detector

• In a typical experiment neutrons are scattered from an aqueous solution of a protein or complex.

• Scattering occurs in a radically symmetric fashion and is measured on a 2D detector.

Q= Scattering vector ki= incident wavevectorKf =scattered wavevector𝜆= neutron wavelength𝜃= scattering wavelength

0 20000 40000 60000 80000 100000 120000 1400000

2

4

6

8

10

12

14

16

18

W

avel

engt

h(A)

Time(s)

The wavelength of incident beam is directly proportional to time.

Determination of Parameters

0.1 1 100.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

Fl

ux o

f neu

trons

(arb

.unit

s 10

6 )

Wavelength(A)

T=4.22K T=77K T=200K T=300K

Maxwell-Boltzmann Distribution for moderator energies of 4.22K, 77K, 200K and 300K

The flux of neutrons at different detector distance.

10 100 1000

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Flu

x o

f n

eu

tro

ns (

arb

.un

its 1

06 )

Number of channels

L= 5m L= 10m L=15m L= 20m L= 25m L= 30m

The flux of neutrons at different detector distance.

50 100 150 200

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Flu

x of

neu

tron

s (a

rb.u

nits

10

6 )

Number of channels

L= 5m L= 10m L=15m L= 20m L= 25m L= 30m

Objects and materials of SANS investigation

•BiologyProteinVirusesLipids aggregate•ChemistryPolymersPrecipitatesColloidsgels

•Material engineeringAlloys Ceramicsglasses

Acknowledgements• The members of the group would like to

thank the following people: Dr. Kuklin , Raul , Islamov and Maria for

their patience and advices. Dr.Noel and NRF for the opportunity given

to us to participate in 2009 SA student summer practice.

All members of the JINR team for their warm hospitality.

THANK YOUFOR

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