Simulations of Chopper Jitter at the LET Neutron Spectrometer at the ...
Simulations of Chopper Jitter at the LET Neutron Spectrometer at the ...
Simulations of Chopper Jitter at the LET Neutron Spectrometer at the ...
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<strong>Simul<strong>at</strong>ions</strong> <strong>of</strong> <strong>Chopper</strong> <strong>Jitter</strong> <strong>at</strong> <strong>the</strong> <strong>LET</strong> <strong>Neutron</strong> <strong>Spectrometer</strong> <strong>at</strong> <strong>the</strong> ISIS TS2 3Figure 2. <strong>LET</strong> chopper and guide layout. Top panel shows <strong>the</strong> chopper distancesand chopper geometry. Bottom panel shows <strong>the</strong> layout <strong>of</strong> <strong>the</strong> guide, with <strong>the</strong> chopperpositions outlined.[7]• The slow Frame Overlap (FO) chopper removes long wavelength neutrons from <strong>the</strong>previous moder<strong>at</strong>or pulse.• The Pulse Removal (PR) chopper selectively removes pulses, to increase pulsesepar<strong>at</strong>ion, by running <strong>at</strong> an integer factor slower than <strong>the</strong> resolution choppers.This is illustr<strong>at</strong>ed in fig. 4, where <strong>the</strong> PR is run <strong>at</strong> half <strong>the</strong> speed <strong>of</strong> <strong>the</strong> resolutionchoppers, to remove every second pulse.• The contaminant removal chopper (CR) removes fast neutrons coming from <strong>the</strong> tail<strong>of</strong> <strong>the</strong> pulse.[4]Illustr<strong>at</strong>ed by simul<strong>at</strong>ion results in figure 4, <strong>the</strong> white beam from <strong>the</strong> short pulsed(4 µs) moder<strong>at</strong>or is separ<strong>at</strong>ed into a few distinct wavelengths by <strong>the</strong> first set <strong>of</strong> fast
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