New Readout Electronics for 3-D Position Sensitive CdZnTe/HgI Detector Arrays

The 4th-generation readout system based on VAS_UM/TAT4 ASICs for 3-D position sensitive CdZnTe/HgI₂ detector arrays has been developed and tested. Each VAS_UM/TAT4 chip is a 129-channel self-triggered monolithic Application Specific Integrated Circuit (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 cmtimes2.2 cm 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 cmtimes2 cm. The detector and the front-end board are connected by three pairs of 42-pin connectors for easy assembly and component replacement. Up to nine detector modules can be plugged into 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 with different dynamic ranges and shaping times were fabricated for gamma-ray spectroscopy in CdZnTe and HgI₂. These are the first ASIC readout systems that allow multiple 3-D position sensitive CdZnTe/HgI₂ detector modules to be tiled together, to achieve a detection volume greater than 50 cm ³ on a single detector plane. Multiple planes of detector arrays can be operated together to achieve more than 100 cm³ detection volume on a single system. In this paper, the VAS_UM/TAT4 ASIC systems are described and their test results are reported