1. Small angle neutron scattering
Students:
Andisiwe Stuurman, University of Fort Hare
Kwindla Nobaza, University of Johannesburg
Merriam Ngulube, University of Limpopo
Project Coordinator: Dr. A.I Kuklin
JINR Summer student practice, 3-23 September 2011, Dubna

2. SANS Introduction
Small Angle Neutron Scattering is a method used to investigate the properties of different materials by scattered neutrons at small angles.
Nuclear fission reaction – one incident neutron hits the target and emits an average of 2.5 neutrons, energy release ~ 180 MeV.
Spallation reaction is one where extremely high energy particles (e.g. protons) hit the target made of a neutron-rich material, “breaking” a heavy nucleus into highly excited fragments

3. Yumo-SANS Instrument(FLNP)
1. Two reflectors 2. Zone of reactor with moderator 3. Chopper 4. First collimator 5. Vacuum tube 6. Second collimator 7. Thermostat 8. Samples table 9. Goniometer Vn-standard 12. Ring-wire detector 13. Position-sensitive detector "Volga” 14. Direct beam detector.

4. SANS: Method of Investigation
In a SANS experiment, the wavelength of the incident beam and the scattering angle define , through the relation expressing momentum conservation in an elastic interaction:
- Q is the wave vector
- λ is the neutron wavelength
- θ is the scattering angle between the direction of the transmitted and scattered beams
The dimension of a probe is D = 2π/Q
The range of Q (scattering vector) is Å-1

5. Applications of SANS
The following types of samples can be analysed using SANS, with applications across various disciplines.
Chemistry:
polymers
precipitates
surfactants
colloids
gels
Biology:
- proteins
- viruses
- lipid aggregates
- emulsificators
Materials science:
alloys
glasses
composites
porous systems
grained materials
ceramics
powders

6. Comparison Advantages disadvantages
The advantages that SANS presents, due to the neutrons’ properties are:
Contrast variation method
Interaction with nuclei
Deep penetration
SANS is expensive.
Neutron flux is very low as compared to X-ray flux.
Interaction of neutrons with matter is weak.
Cannot be operated at small scale.

7. Project objectives
Verifying the spherical shell-like structure of apoferritin with SANS method of investigation
Determine the parameters of the structure:
Radius of gyration
Inner and outer radii
Use of different programs (Fitter 2.1.5, Primus, Origin 8.5) in order to compare the results

8. Determining Rg using Primus

9. Determining Rg using Origin

10. Determining inner and outer radii using Fitter

11. Conclusion
From the experimental data gathered from the YuMO SANS Instrument we obtained the experimental curves;
Using Primus and Origin we determined the radius of gyration of apoferritin and compared them, obtaining similar results;
Successfully modeled the experimental plot with Fitter, thus obtaining the inner and outer radii for our sample;
Apoferritin has a spherical shell-like structure

12. References
L.A. Feigin, D I. Svergun, Structure Analysis by X-Ray and Neutron Scattering
J.Teixiera., Introduction to SANS applied to colloidal science.
Alexander Ioffe, Neutron Sources., Vol 15.,University Munster

13. Acknowledgements DST and NRF
We would like to thank Dr A.I Kuklin and his team from Frank Laboratory of Neutron Physics.
Also we would like to extend our gratitude to the organizers of the Summer Student Practice.(JINR, Dr Jacobs, Prof. Lekala)

14. THANK YOU FOR YOUR KIND AUDIENCE!