Development of Proton Detection System with Thin Ruby Scintillator Insensitive to Neutrons and Gamma Rays for Neutron Lifetime Measurement

A proton detector for lifetime measurement of neutrons using a thin ruby scintillator which can be used under an environment of neutrons and γ-rays has been developed. The detector is almost insensitive to neutrons and γ-rays. This was confirmed by setting the detector adjacent to the ultra-cold neutron (UCN) facility installed in Kyoto University Reactor. When a single proton was injected into the scintillator, many scintillation signals were observed. The number of scintillation signals decreases with decreasing proton energy. Although the output signals generated by the scintillation and by the dark currents of a photomultiplier have approximately the same pulse heights, the proton can be detected by counting the signals within the time width corresponding to the decay time of scintillation. This neutron lifetime measurement system can be applied to the detection of particles other than protons.