Performance evaluation for a radiation imaging detector using single-crystal GPS (Ce) plate

Cerium doped gadolinium pyrosilicate (GPS (Ce), Gd2Si2O7), which is a scintillator with a high light output, is a likely candidate to develop high-resolution radiation imaging detectors. Thus we fabricated a GPS (Ce) imaging detector using a single-crystal GPS (Ce) plate in combination with a position-sensitive photomultiplier tube (PSPMT). Through a performance evaluation, we found that the spatial resolution was ~ 0.5 mm FWHM for Am-241 α particles (5.5 MeV) with an energy resolution of 15% FWHM. The decay time difference of GPS (Ce) between 5.5 MeV α particles and 662 keV Cs-137 γ photons was 7 ns, which was insufficient to separate each image using pulse-shape discrimination. However, the α/γ ratio was large (0.35), so it was possible to separate 5.5 MeV α particles and 662 keV Cs-137 γ photons by the energy spectra. We conclude that the imaging detector using single-crystal GPS (Ce) is promising for radiation, especially for α particles.