Evaluation of properties of YAG (Ce) poly-crystal scintillator with APD

Abstract

With future space applications in mind, basic properties of two poly-crystal Y3Al5O12 (YAG) scintillators were studied. One has a diameter of 17 mm and a thickness of 2.4 mm, doped with Ce at 0.5 mol percent. The other has a diameter of 16 mm and a thickness of 0.75 mm, 0.8 mol percent. For comparison, a single-crystal YAG (25 mm in diameter and 40 micrometers in thickness) was also measured. Optical spectroscopy indicates that the poly- and single-YAGs have essentially the same absorption features (at 230, 340, and 460 nm) due to Ce, but their emission spectra (peaked at 525 to 540 nm) may be slightly different. When coupled to a phototube (Hamamatsu R6231), and irradiated by 662 keV gamma-rays, the two poly-YAGs exhibited somewhat higher light yields (approximately 40 percent of CsI:Tl) than the single-YAG, together with an FWHM energy resolution of 8.0 percent. A smaller (5 x 5 x 5 cu mm) poly-YAG, with 0.5 mol percent Ce doping, was also studied with avalanche photodiode (Hamamatsu S8664-55). At - 20 C and a bias voltage of approximately 300 V, an improved energy resolution of 6.3 percent was achieved for the 662 keV gamma-rays.