Tuning of Nuclear Spectroscopic Telescope Array (NuSTAR) Application Specific Integrated Circuits (ASICs) to improve low energy threshold of future Hard X-ray Imaging Detectors

TL;DR

This paper discusses tuning and optimizing Application Specific Integrated Circuits (ASICs) for the NuSTAR mission to enhance low energy detection capabilities in future X-ray imaging detectors, focusing on gain settings and charge pump mode adjustments.

Contribution

It introduces a semi-automated procedure for tuning NuASIC parameters to improve low energy thresholds in HREXI detectors, adapting the ASIC for broader energy ranges.

Findings

Optimal ASIC parameters identified for low energy threshold

Charge Pump Mode effectively reduces electronics noise

Procedure accelerates detector integration process

Abstract

Detector commanding, processing and readout of spaceborne instrumentation is often accomplished with Application Specific Integrated Circuits (ASICs). The ASIC designed for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission (NuASIC) enables future tiled CdZnTe (CZT) detector array readout for x-ray detectors such as the High Resolution Energetic X-ray Imager (HREXI). Modified NuASIC gain settings have been implemented for HREXI's broader targeted imaging energy range (3-300 keV) compared to NuSTAR (2-79 keV), which may require updated NuASIC internal parameters for optimal energy resolution. To reach HREXI's targeted low energy threshold, we have also enabled the NuASIC's "Charge Pump Mode" (CPM), which introduces an additional tuning parameter. In this paper, we describe the mechanics of the NuASIC's adjustable parameters and use our recently developed ASIC Test Stand (ATS) to probe a "bare" NuASIC using its internal test pulser. We record the effects of parameter tuning on the device's electronics noise and low energy threshold and report the optimal set of parameters for HREXI's updated gain setting. We detail a semi-automated procedure to derive the optimal parameters for each of HREXI's large area, closely tiled NuASIC/CZT detectors to expedite instrument integration.