Development of a 32-channel ASIC for an X-ray APD Detector onboard the ISS

TL;DR

This paper presents a 32-channel ASIC designed for X-ray detection using APDs on the ISS, achieving low noise, wide energy range detection, and space radiation tolerance.

Contribution

The paper introduces a novel 32-channel ASIC with low-noise, high dynamic range, and space radiation tolerance for APD-based X-ray detection in space applications.

Findings

Achieved a minimum energy detection threshold of 20 keV.

Demonstrated an energy resolution of 6.7% at 662 keV.

Confirmed space radiation tolerance through proton beam testing.

Abstract

We report on the design and performance of a mixed-signal application specific integrated circuit (ASIC) dedicated to avalanche photodiodes (APDs) in order to detect hard X-ray emissions in a wide energy band onboard the International Space Station. To realize wide-band detection from 20 keV to 1 MeV, we use Ce:GAGG scintillators, each coupled to an APD, with low-noise front-end electronics capable of achieving a minimum energy detection threshold of 20 keV. The developed ASIC has the ability to read out 32-channel APD signals using 0.35 $\mu$m CMOS technology, and an analog amplifier at the input stage is designed to suppress the capacitive noise primarily arising from the large detector capacitance of the APDs. The ASIC achieves a performance of 2099 e$^{-}$ + 1.5 e$^{-}$/pF at root mean square (RMS) with a wide 300 fC dynamic range. Coupling a reverse-type APD with a Ce:GAGG scintillator, we obtain an energy resolution of 6.7% (FWHM) at 662 keV and a minimum detectable energy of 20 keV at room temperature (20 $^{\circ}$C). Furthermore, we examine the radiation tolerance for space applications by using a 90 MeV proton beam, confirming that the ASIC is free of single-event effects and can operate properly without serious degradation in analog and digital processing.