COMPARISON BETWEEN PULSED AND CONTINUOUS SOURCES FOR SMALL ANGLE NEUTRON SCATTERING (SANS) Tjatji Tjebane, Dolly Langa, Lolan Naicker, Daphney Singo Joint

COMPARISON BETWEEN COMPARISON BETWEEN PULSED AND CONTINUOUS PULSED AND CONTINUOUS

SOURCES FOR SOURCES FOR SSMALL MALL AANGLE NGLE NNEUTRON EUTRON SSCATTERING (SANS)CATTERING (SANS)

Tjatji Tjebane, Dolly Langa, Lolan Naicker, Tjatji Tjebane, Dolly Langa, Lolan Naicker, Daphney SingoDaphney Singo

Joint Institute for Nuclear Research, Dubna – South African StudentS Summer Practice 2008

Supervisor: Aleksander Kuklin

OUTLINE Introduction

SANS Principles

Contrast Variation Method

Neutron Sources

IBR-2 and ILL Fission Reactors

SANS Equipment

Main Parameters of YuMO and D22 Instruments

Typical SANS Application

Remarks

Acknowledgements

04/19/2304/19/23 22SA-JINR Summer School 2008SA-JINR Summer School 2008

Neutron scattering is the process of collision between neutrons emitted by a

source and a target which is the studied sample.

When the scattering angles of these collisions are very small (the emerging

beam is very close to the axis of the emitted neutrons), it is referred to as

Small Angle Neutron Scattering (SANS)

Why Neutrons? No charge, very penetrating, and non destructive to samples Neutron wavelengths are comparable to atomic sizes and inter-distance

spacing Neutron interactions with hydrogen and deuterium are widely different

making the deuterium labeling method an advantage

INTRODUCTION


SANS PRINCIPLE

thicknessSample

angle Solid

section-cross aldifferenti Sample

ion transmissSample

,efficiencyDetector )(

fluxIncident )(0

fluxneutron Scattered , Where

)()(0

),(

d

dd

T

I

I

dddTII

d I

0I

04/19/2304/19/23 44

CONTRAST VARIATION METHODCONTRAST VARIATION METHOD

Contrast is the difference in the scattering length density () values between that part of

the sample of interest (p), and the surrounding media or matrix (m), i.e.

p m

When the contrast is zero, the scattering bodies are said to be at contrast matching.

For example, a sample containing three compounds. Using contrast matching,

the contrast between the two parts could be erased, allowing analysis of the third

compound.


NEUTRONS SOURCES

Fragmentation Source

• 2.5 neutrons per event

•1 neutron consumed in sustaining reaction

• 0.5 absorbed

• High power load per neutron (~ 180 MeV)

Spallation source

• High energy incoming particle (typically

protons)

• Heavy metal target (Ta, W, U, e.t.c)

• Neutrons cascade

• >10 neutrons per incident proton

• Low power load per outgoing neutron (~ 55 MeV)

04/19/2304/19/23

Radioactive Sources

Nuclear Explosions

• Californium-252

A typical Cf-252 neutron source emits between 1×107 to 1×109 neutrons per second

It results from a rapid release of energy from an intentionally high-speed nuclear reaction.

The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading

combination


IBR-2 and ILL Fission Reactors

Pulsed Beam Reactor

Power output ~ 2 MW

1 X 1016 neutrons/(cm2.s)

IBR-2 ILL

Continuous Beam Reactor

Power output ~ 58 MW

1.5 x 1015 neutrons/(cm2.s)


SANS EQUIPMENT AT FLNP (JINR) AND ILL (Grenoble)

YuMO

04/19/2304/19/23 99SA-JINR Summer School 2008SA-JINR Summer School 2008 (D22)

MAIN PARAMETERS OF

YUMO AND D22 INSTRUMENTS

04/19/2304/19/23 1010

Name of parameter YuMO D22

1 Flux at sample ~ 107 x 107 n.cm2.s1 ~ 1.2 x 108 n.cm2s1

2 Q-Range 7x103 0.5 Å-1 4 x 104 to 0.44 Å1

3 Dynamic Q-Range 7x103 0.5 Å1 _____

4 Used wavelength 0.5A to 8A 4.5 to 40 Å

5 Calibration standard Vanadium (during the experiment) H20 (Placed in sample position)

6 Resolution 5 10 % 5 10 %

7 Pulse repetition frequency 5 Hz Continuous

8 Specific features

Two detector systems:He3 filled, home made , 8 independent

wires.Direct beam: 6Li-convertor (home made

preparation)

One large area detector system (1m2) movable (

Biology

• Organization of biomolecular complexes in solution

• Mechanisms and pathways for protein folding

Polymers

• Conformation of polymer molecules in solution

• Structure of microphase for separated block polymers

Chemistry

• Structure and interactions in colloid suspensions

• Mechanisms of molecular self-assembly in solutions

Materials Engineering

• Analysis of ferrofluids

•Crystalline structure investigations

TYPICAL SANS APPLICATIONS INCLUDE


REMARKS


ACKNOWLEDGEMENT

The authors would like to acknowledge the following:The authors would like to acknowledge the following: Kuklin Aleksander Kuklin Aleksander Murugova Tat’yanaMurugova Tat’yana Kovalev YuriiKovalev Yurii Raul ErhanRaul Erhan

All of the above from the YuMO Group, Condensed Matter DepartmentAll of the above from the YuMO Group, Condensed Matter Department

We would also like to extend our regards to the organizer of the We would also like to extend our regards to the organizer of the Summer Student Practice and all members of the JINR involved in this Summer Student Practice and all members of the JINR involved in this project.project.


THANK YOU!!!THANK YOU!!!


Documents

COMPARISON BETWEEN PULSED AND CONTINUOUS SOURCES FOR SMALL ANGLE NEUTRON SCATTERING (SANS) Tjatji Tjebane, Dolly Langa, Lolan Naicker, Daphney Singo Joint