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Resolution function for small angle neutron scattering. Khaled Gad Mostafa ashshoush supervisor Dr.Alexander Kuklin. Neutron sources.
Khaled Gad Mostafa ashshoushsupervisor Dr.Alexander Kuklin
Since the early days of neutron scattering, there has been an insatiable demand for higher neutron fluxes. Neutron sources are based on various processes that liberate excess neutrons in neutron rich nuclei such as Be, W, U, Ta or Pb. Presently, the highest fluxes available are around a few 1015 n/cm2 sec. Even though various neutron sources exist, only a few are actually useful for scattering purposes. These are:
1- continuous reactors
2- spallation sources
3- some other neutron sources.
Most of nuclear reactors is continuous fission mode reactor which neutrons are
one of the fission products, the intensities of the neutron at the sample and the detector are as in the following fig
Universitatea din Bucuresti, Facultatea de Fizica, Septembrie 2008
1- Neutrons interact through short-range nuclear interactions. They are very penetrating and do not heat up (i.e., destroy) samples.
2-Neutron wavelengths are comparable to atomic sizes and inter-distance spacing.
3-Neutron energies are comparable to normal mode
energies in materials (for example phonons, diffusive
modes). Neutrons are good probes to investigate the
dynamics of solid state and liquid materials.
1-Neutron sources are very expensive to build and to maintain.
YuMO Spectrometer: 1 – reflectors;
2 – chopper; 4,6 – collimator;
8 – sample table; 11,12 – detectors;
14 – direct beam detector
IBR – 2 Reactor
S1≈ 2 S2
3m – 16m
1m – 15m
Optimized for ~ ½ - ¾ inch diameter sample
J. Texeira, Introduction to Small Angle Neutron Scattering Applied to Colloidal Science, Kluwer Academic Publishers, Netherlands, 1992
Instrumental smearing affects SANS data. In order to analyze smeared SANS data, either desmearing of the data or smearing of the fitting model function is required
Instrumental smearing is represented by the following 1D convolution smearing integral (suitable for radially averaged data):
the 1D resolution function is defined as a Gaussian function:
σQis the Q standard deviation.
In order to express σQ, differentiate Q on both sides:
Take the square:
SANS resolution has three contributions
The authors would like to acknowledge the following:
All of the above from the YuMO Group, Condensed Matter Department
We would also like to extend our regards to the organizer of this Practice and all members of the JINR involved with this project.