Investigation of neutron scattering in the Multi-Blade detector with Geant4 simulations

Abstract

The European Spallation Source (ESS) is the world's next generation spallation-based neutron source. The research conducted at ESS will yield in the discovery and development of new materials including the fields of manufacturing, pharmaceuticals, aerospace, engines, plastics, energy, telecommunications, transportation, information technology and biotechnology. The spallation source will deliver an unprecedented neutron flux. In particular, the reflectometers selected for construction, ESTIA and FREIA, have to fulfill challenging requirements. Local incident peak rate can reach 10$^5$~Hz/mm$^2$. For new science to be addressed, the spatial resolution is aimed to be less than 1 mm with a desired scattering of 10$^{-4}$ (peak-to-tail ratio). The latter requirement is approximately two orders of magnitude better than the current state-of-the-art detectors. The main aim of this work is to quantify the cumulative contribution of various detector components to the scattering of neutrons and to prove that the respective effect is within the requirements set for the Multi-Blade detector by the ESS reflectometers. To this end, different sets of geometry and beam parameters are investigated, with primary focus on the cathode coating and the detector window thickness.