A Scalable, Mosaicked CdZnTe (CZT) Detector Plane Architecture for Next-Generation Time Domain and Multi-messenger Astrophysics

The High Resolution Energetic X-ray Imager (HREXI) is a scalable detector plane architecture built around the NuSTAR ASIC (NuASIC) for the independent and simultaneous readout of large arrays of pixelated CdZnTe (CZT) detectors, with a pixel pitch of 604.8 μm over a 2 cm × 2 cm active area and sensitive between 3 to 600 keV, with higher energies extending to MeV energies possible depending on the thickness of the CZT crystals used. The hierarchical architecture is made up of 3 primary layers: (1) the detector crystal array (DCA) which supports the operation of a 2 × 2 array of NuASIC enabled detectors; (2) the FPGA mezzanine board (FMB) which supports the operation of a tiled 4 × 4 array of DCAs, or 16 total detectors; and (3) the detector module board (DMB) which controls and collects data form 8 chains of 8 FMBs, a total of 1024 individual detectors with an active area of approx. 4096 cm². Here we present: (1) an overview of the prototype detector system, consisting of 128 cm² of detector area contained within 8 DCAs on a single readout chain, (2) detector system performance as a function of temperature under TVAC, (3) performance improvements made possible by firmware upgrades enabling FWHM energy resolutions of 0.84 keV @ 5.9 keV, (4) the high resolution 2D imaging calibration of the detector plane at 100 μm resolution, (5) overview of the status of flight qualification and (6) an overview of future development and deployment plans in the next generation of high angular resolution (5′) wide-field imagers to support time-domain astrophysics in the next decade.