FLUKA simulations and benchmark measurements of the YAP(Ce) scintillators installed on the VESUVIO spectrometer

Abstract We present experimental results and FLUKA Monte-Carlo simulations reproducing the counting efficiency and the energy resolution of the cerium-activated yttrium-aluminium-perovskite photon detectors installed on the VESUVIO neutron spectrometer at the ISIS Pulsed Neutron and Muon Source. In particular, we investigate the performance of these detectors in the energy range between 100 keV and 300 keV. In this range, the γ -emission of the 197Au resonant analyser foils, installed on VESUVIO to select the energy of scattered neutrons, is predominant. Such photons are currently discarded by the low-level discrimination threshold of the acquisition electronics set to 600 keV. Here, we model the detector crystals for a series of thickness values, and we discuss how 2-cm-thick crystals would significantly reduce the acquisition times with respect to the 6-mm-thick crystals employed at present. Additionally, we show how the signal-to-background ratio can be substantially enhanced by shielding the scintillators with 0.5-mm-thick Pb foils. We finally discuss the improved detection performance on a model sample of interest for Cultural-Heritage applications.