A frontend LSI for large-area gamma-ray imaging detectors with gas electron multipliers

A prototype frontend LSI for gamma-ray detectors with GEM (Gas Electron Multiplier) foils has been designed and fabricated. For reduction of number of channels and fast readout, we adopted X- and Y-strip readout method. Obtained charges are converted to digital by 10-bit 10Msps pipelined ADCs on the chip. In order that the ghost images are reduced, which are the drawback of the X- and Y-strip method, simple time-to-digital converters are designed on the same chip. The chip with 9 channels has been designed and fabricated with the TSMC 0.25¿m process. With the obtained ASIC chips, quick tests have been performed.