Low-power Wide-dynamic-range Readout System for a 64-channel Multi-anode PMT of a Scintillation Gamma Camera

We have developed a low-power wide-dynamic-range readout system for a 64-channel multi-anode photomultiplier (PMT) of a scintillation gamma camera. Each anode is individually read with the system that contains discrete devices of amplifiers, comparators, sample-hold ADCs, and FPGAs. The size of the system which is designed for a two-dimensional array of Hamamatsu flat panel PMT H8500 is 5x5x14 cm(3). The input dynamic range is variable by replacing the feedback capacitor of the preamplifier (e.g., 700 pC and 4000 pC for GSO(Ce) and LaBr3(Ce) crystals, respectively). The serialized ADC data are sent to a VME sequence module. The total power consumption is 1.6 W per 64 channels. With this system we have developed a gamma camera using an 8x8 array of GSO(Ce) pixels with a pixel size of 6x6x13 mm(3) coupled to an H8500, and obtained flood-field irradiation images at energies from 30 keV to 1.3 MeV. The energy resolution was 10.8 +/- 0.4% (FWHM) at 662 keV. In addition, we used the readout system for an 8x8 array of LaBr3(Ce) pixels with a pixel size of 6x6x15 mm(3) and obtained a flood-field irradiation image at 662 keV.