VAS/spl I.bar/UM/TAT4 ASIC readout systems for 3D CdZnTe/HgI/sub 2/ detector arrays

The 4th-generation readout systems based on VAS_UM/TAT4 ASICs for 3-D position sensitive CdZnTe/HgI₂ detector arrays have been developed and tested. Each VAS_UM/TAT4 chip is a 129-channel self-triggered monolithic application specific integrated circuitry (ASIC). One 3-D position-sensitive detector module consists of one CdZnTe or HgI₂ gamma-ray spectrometer, and one VAS_UM/TAT4 ASIC mounted on a 2.2 times 2.2 cm² front-end board. Each detector has an array of 11 by 11 pixel anodes fabricated on the anode surface with an area up to 2 by 2 cm². The detector and the front-end board are connected by three pairs of 42-pin connectors for easy assemble and component replacement. Up to nine detector modules can be plugged in to a single motherboard to form a 3 by 3 detector array. The VAS_UM/TAT4 chip can read out both the amplitude of induced charge on each electrode and the electron drift time needed for reconstructing energy deposition and three-dimensional coordinates of each radiation interaction. Three different sets of VAS_UM/TAT4 chips were fabricated - the first set is for intermediate energy gamma-ray spectroscopy on CdZnTe with a dynamic range up to 1 MeV per channel. The second set is for higher-energy gamma-ray detection in CdZnTe for energy deposition of up to 3 MeV per channel, and the third set is for HgI₂ gamma-ray spectrometers (up to 1 MeV per channel). These are the first ASIC readout systems that allow multiple 3-D position sensitive CdZnTe/HgI₂ detector modules to be tiled together, to achieve detection volume greater than 50 cm³ on a single detector plane. Multiple planes of detector arrays can be operated together to achieve more than 100 cm³ detection volume and beyond on a single system. In this paper, VAS_UM/TAT4 ASIC systems are described and their test results will be reported