Detection of ultracold neutrons with powdered scintillator screens

Abstract: Zinc sulfide (ZnS:Ag) scintillators are widely used for ultracold neutron (UCN) detection, but their application is limited by long decay times and pronounced phosphorescence. We tested two possible replacement scintillators: yttrium aluminum perovskite (YAP:Ce) and lutetium yttrium orthosilicate (LYSO:Ce). Both have decay times on the order of 30-40 ns, which can help reduce dead time in high count rate experiments. YAP:Ce showed a 60% lower phosphorescence when compared to ZnS:Ag after 2 days and outperformed ZnS:Ag in counting UCN by about 20%. On the other hand, LYSO:Ce exhibited more phosphorescence and produced fewer UCN counts compared to both ZnS:Ag and YAP:Ce. Both of these scintillators are viable UCN detectors for high count rate experiments, but YAP:Ce outperformed LYSO:Ce by every tested metric.