Conceptual design of a radial collimator for MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source

Abstract

A parametrized conceptual design for a radial collimator in a neutron backscattering instrument is presented, with application to the characteristic geometry of the MIRACLES spectrometer, that will be constructed at the European Spallation Source (ESS). The analytic development of this design has considered both the forward scattering (sample-analyzer) and backscattering (analyzer-detectors) pathways. All the characteristic dimensions (internal and external radii, slit angle) and figures of merit (such as transmission and estimated background reduction) of the device are calculated as a function of the focal points. Finally, the estimated performance of the final concept has been validated by Monte Carlo simulations.