The Performance Characteristics of the NRL2 ASIC Designed for the Compton Spectrometer and Imager Small Explorer (COSI-SMEX) Telescope

Gamma-ray astrophysics is now a mature science that is motivating significant technological developments in radiation detectors and mixed-signal processing. Advancing the science capabilities of gamma-ray instruments often motivates the push for higher channel density while maintaining low-power, low-noise, front-end electronics. In this regard, the Compton Spectrometer and Imager (COSI), an all-sky surveying MeV gamma-ray Compton telescope selected as a Small Explorers mission (SMEX) that is scheduled for launch in 2025, has implemented the use of application-specific integrated circuits (ASICs) in order to meet the performance demands and science requirements of the telescope. The NRL2 (Naval Research Laboratory 2) is a recently developed 32-channel front-end ASIC that features low-power, low-noise charge preamplification, with 4 configurable gain settings, dual fixed fast and configurable slow shapers per channel for optimized timing and energy resolution, trimmable per-channel discrimination, time-to-analog conversion, and peak detect output. The NRL2 has been instrumented with a high-purity germanium (HPGe) dual-sided strip detector where the detector and ASIC performance have been highly characterized. We present an overview of the readout electronics developed for the COSI-SMEX mission, we report the energy resolution capabilities of this system to be 2.4 keV FWHM at 59.54 keV with a gain setting of 18.4 mV/fC and a peaking time of 2 μs, and discuss preliminary results of our currently ongoing research.