A silicon analyser for the OSIRIS spectrometer: An analytical and Monte Carlo simulation study

Journal article, 2019

The indirect time-of-flight near-backscattering spectrometer OSIRIS at the ISIS Facility is being upgraded with the addition of a silicon analyser. The new analyser bank will allow to increase the dynamic range, giving access to relaxation times up to 400 ps, and provide a further dimension in momentum transfer detection with the help of position-sensitive detectors. Here we present analytical calculations for the energy resolution and an extensive Monte Carlo simulation study to assess the performance of the new analyser bank. Simulation and calculation agree perfectly and confirm the initial design parameters of the spectrometer. The simulations predict similar detected intensity but with a higher resolution compared to the existing analyser setup using pyrolytic graphite crystals. Furthermore, the simulations stress the importance of the sample height for this setup and point toward a necessary further upgrade of the guide system. Further improvements of the energy resolution might be achieved with a pulse shaping chopper.