High-Energy Neutron Response of the HR-GAGG Scintillation Crystal

We report on the high-energy neutron response of the HR-GAGG crystal. High-energy Resolution (HR) GAGG (Gd 3 Al 2.6 Ga 2.4 O 12 :Ce) is a relatively new scintillation crystal that provides a high density, a high light output, a fast decay time and is not hygroscopic. Aside from its use for gamma-ray spectroscopy, the GAGG scintillator has been investigated for the detection and discrimination of both alpha particles and neutrons. Gamma-ray/alpha-particle discrimination is possible via pulse shape discrimination (PSD) techniques; thermal neutron detection is possible via measurement of the gamma-ray emission associated with thermal neutron capture on stable Gd isotopes from specifically shielded GAGG crystals. To our knowledge, the direct detection of fast neutrons using GAGG, or any variant of GAGG, has yet to be reported. Our results show the ability of the HR-GAGG crystal to perform PSD when irradiated by high-energy neutron beams. We performed these tests at the UC-Davis Crocker Nuclear Laboratory cyclotron. The result of four different endpoint energy neutron beams, ranging from 14.1 MeV - 60.5 MeV, irradiating the HR-GAGG crystal yielded two discernable bands of events attributed to fast neutrons and gamma rays from the cyclotron. Lower energy neutrons - from the beam (1.9 MeV) or using laboratory neutron/gamma-ray sources (e.g., 252Cf) - demonstrates no discernable signature of neutron detection and discrimination. We show results from the low- and high-energy neutrons beams interacting with the HR-GAGG and discuss the isotopes responsible for the high-energy neutron capabilities of this material.