COMPARISON BETWEEN PULSED AND CONTINUOUS SOURCES FOR SMALL ANGLE NEUTRON SCATTERING (SANS) Tjatji Tjebane, Dolly Langa, Lolan Naicker, Daphney 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 9/21/20152 SA-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 9/21/20153 SA-JINR Summer School 2008

SANS PRINCIPLE 9/21/20154

CONTRAST 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. 9/21/20155 SA-JINR Summer School 2008

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) 9/21/2015

 Radioactive Sources  Nuclear Explosions Californium-252 A typical Cf-252 neutron source emits between 1×10 7 to 1×10 9 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 9/21/20157 SA-JINR Summer School 2008

IBR-2 and ILL Fission Reactors Pulsed Beam Reactor Power output ~ 2 MW 1 X neutrons/(cm 2.s) IBR-2ILL Continuous Beam Reactor Power output ~ 58 MW 1.5 x neutrons/(cm 2.s) 9/21/20158 SA-JINR Summer School 2008

SANS EQUIPMENT AT FLNP (JINR) AND ILL (Grenoble) YuMO 9/21/20159 SA-JINR Summer School 2008 (D22)

MAIN PARAMETERS OF YUMO AND D22 INSTRUMENTS 9/21/ Name of parameterYuMOD22 1Flux at sample ~ 10 7  x 10 7 n.cm  2.s  1 ~ 1.2 x 10 8 n.cm  2 s  1 2Q-Range 7x10  3  0.5 Å -1 4 x 10  4 to 0.44 Å  1 3Dynamic Q-Range 7x10  3  0.5 Å  1 _____ 4Used wavelength0.5A to 8A4.5 to 40 Å 5Calibration standardVanadium (during the experiment)H 2 0 (Placed in sample position) 6Resolution 5  10 % 7Pulse repetition frequency5 HzContinuous 8Specific features Two detector systems: He 3  filled, home made, 8 independent wires. Direct beam: 6Li-convertor (home made preparation) One large area detector system (1m 2 ) 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 9/21/ SA-JINR Summer School 2008

REMARKS 9/21/ SA-JINR Summer School 2008

ACKNOWLEDGEMENT The authors would like to acknowledge the following:  Kuklin Aleksander  Kuklin Aleksander  Murugova Tat’yana  Kovalev Yurii  Raul Erhan All of the above from the YuMO Group, Condensed Matter Department  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 project. 9/21/ SA-JINR Summer School 2008

THANK YOU!!! 9/21/ SA-JINR Summer School 2008