Simulations of Chopper Jitter at the LET Neutron Spectrometer at the ...

Simulations of Chopper Jitter at the LET Neutron Spectrometer at the ISIS TS2 8(a) Zero jitter(b) 2 µs jitter(c) 10 µs jitter(d) 20 µs jitterFigure 6. A virtual experiment: Detector output when scattering off a vanadiumsample of radius 1 cm, with both beam choppers running at 140 Hz, and with 4different jitter settings.5. Discussion and ConclusionWe have conducted a detailed simulation of the LET spectrometer. We find that theinstrument performs in general as expected.As can be seen in fig. 9, jitter values at or below 2 µs have less than 1 % effect onthe instrument resolution, judged from virtual experiments of elastic scattering, withthe chopper speed set at 250 Hz. In comparison, the jitter when running the actualLET resolution choppers at the same speed, is at 0.4 µs. The simulated degradation ofresolution at this jitter is well below the statistical uncertainty (0.04 %) of the simulationresults.In conclusion, our simulations show that jitter will have negligible effect on theperformance of the actual LET instrument. In cases where a lorentzian tail in theresolution function is particularly detrimental, a more careful analysis is needed.Simulation of jitter effects on future designs of high resolution instruments could lead to