Evaluation of properties of YAG (Ce) ceramic scintillators

Abstract

We measured basic properties of three ceramic Y/sub 3/Al/sub 5/O/sub 12/ (YAG) scintillators doped with Ce to a concentration of 0.5, 0.05, and 0.005 mol%, in comparison with a monocrystalline YAG scintillator with unknown amount of Ce doping. First, optical transparency and emission spectra were investigated. We confirmed that the transparency of the ceramics is comparable to that of the monocrystalline one (/spl sim/80%) in wavelengths longer than /spl sim/500 nm. The ceramics did not show an indication of lattice defects which is present in the monocrystalline YAG. Then the response to /spl gamma/-rays was studied using a phototube as a scintillation light detector. The 0.5 mol% sample exhibited the highest light yield (/spl sim/40% of CsI), with an energy resolution of about 7.2% at /sup 137/Cs 662 keV photoabsorption peak. The optimum Ce concentration for a /spl sim/2 mm thick ceramic YAG was determined to be /spl sim/0.1 mol%. Using the delayed coincidence method, the principal time constant of the ceramic YAGs was measured as /spl sim/80 ns. By irradiating 5.49 MeV /spl alpha/-particles, the /spl alpha/-ray to /spl gamma/-ray light yield ratio of the ceramic YAGs was found to depend negatively on the amount of Ce; namely, 0.28, 0.20, and 0.13 in the increasing order of the Ce concentration. The 200-1000 keV intrinsic background of the 0.5 mol% ceramic was /spl sim/10/sup -5/ counts/s/cm/sup 3/, indicating that it is not significantly contaminated by radioactive impurities.