Monte Carlo simulation of crystal monochromators/analysers – Applications for the crystal-analyser neutron spectrometer IRIS

It is shown that Monte Carlo simulations of a crystal monochromator/analyser by means of the Virtual Instrumentation Tool for ESS (VITESS) offer a correct basis for the computation of the resolution function of crystal analyser spectrometers. Relying on comparisons of MC computed and measured data of vanadium and superfluid helium, a bench marking of the programme codes of IRIS was performed practically limited only by the statistics of the experimental calibration data. Recent results from the study of the input time pulses from the liquid hydrogen moderator and pulse-shaping choppers are also mentioned.