Development of large area gamma-ray camera with GSO(Ce) scintillator arrays and PSPMTs

摘要

We have developed a position-sensitive scintillation camera with a large area as an absorber of an advanced Compton gamma-ray camera. At first we tested GSO(Ce) crystals. We compared light output from the GSO(Ce) crystals under various conditions: the method of surface polishing, the concentration of Ce, and co-doping Zr. As a result, we chose the GSO(Ce) crystals doped only 0.5 mol% Ce, surface of which was polished by chemical etching for the scintillator of our camera. We also made a 16 x 16 cm~2 scintillation camera which consisted of nine position-sensitive PMTs (PSPMTs Hamamatsu flat-panel H8500 ), the each of which had 8 x 8 anodes with a pitch of 6 mm and coupled to 8 x 8 arrays of pixelated 6 x 6 x 13 mm~3 GSO(Ce) scintillators. For the readout system of 576 anodes of the PMTs, we used chained resistors to reduce the number of readout channels down to 48 for saving power consumption. The camera has the position resolution of less than 6 mm and a typical energy resolution of 10.5% (FWHM) at 662 keV at each pixei in a large area of 16 x 16cm~2. Furthermore, we constructed a 16 x 16 array of 3 x 3 x 13 mm~3 pixelated GSO(Ce) scintillators, and glued it to a PMT H8500. This camera had the position resolution of less than 3 mm in area of 5 x 5 cm~2, except for some of edge pixels; the energy resolution was typically 13% (FWHM) at 662 keV.