A thesis submitted 2015 for the degree of Doctor of Philosophy and defended January 29, 2015.
The PhD School of Science
Faculty of Science, Niels Bohr Institute, X-ray and Neutron Science, University of Copenhagen, Denmark
Development of Instrumentation for Spin-Echo Induced Spatial Beam Modulations
for Small Angle Scattering Investigations
Spin-Echo Modulated Small Angle Neutron Scattering in Time-of-Flight mode (ToF SEMSANS) is an emerging technique extending the measurable phase space covered by neutron scattering. Using inclined magnetic field surfaces, (very) small angle scattering from a sample can be mapped into the spin orientation of the neutron as it has been shown in Spin-Echo Small Angle Neutron Scattering (SESANS).
Taking this technique further we have shown that it is possible to perform quantitative Dark-Field Imaging, where the small angle scattering signal of individual areas in a neutron image can be obtained. This was done by using triangular shaped magnetic fields to create a spatially modulatedbeam after the spin analyser, and mapping the small angle scattering signal into a dampening of the amplitude of the beam modulation.
The first progress we made was to construct the SEMSANS instrument at the Reactor Institute Delft, TUDelft, and resolve the modulation using absorption gratings in front of a detector without spatial resolution, i.e. a simple counting detector. Combining this with a virtual copy of the instrument, built using the Monte Carlo Ray-Tracing simulation package McStas, we were able to expand our investigations beyond the instrumental limitations at the time in order to examine the effect of restoring the SpinEcho condition.
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