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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. SANS Introduction.
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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
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
Yumo-SANS Instrument(FLNP) 1. Two reflectors2. Zone of reactor with moderator3. Chopper4. First collimator5. Vacuum tube6. Second collimator7. Thermostat8. Samples table9. Goniometer10-11. Vn-standard12. Ring-wire detector13. Position-sensitive detector "Volga”14. Direct beam detector.
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 0.001--1 Å-1
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
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.
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
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
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 • http://www.engr.sjsu.edu/rkwok/phys275/.ppt • http://www.ncnr.nist.gov/programs/sans/ • http://www.jinr.ru
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)
