Development of Dual-Gain SiPM Boards for Extending the Energy Dynamic Range

TL;DR

This paper presents the development of dual-gain SiPM boards to extend the energy dynamic range of gamma-ray calorimeters, addressing non-linearity issues and enabling detection across a broad energy spectrum for astrophysical applications.

Contribution

It introduces dual-gain SiPM boards using two SiPM species to significantly increase the energy range coverage of scintillator-based calorimeters in gamma-ray detection.

Findings

Demonstrated extended energy range from 2.5 to 30 MeV with dual-gain SiPMs.

Showed sensitivity to 60 MeV protons using the developed system.

Validated the concept with high-energy gamma-ray and proton beam tests.

Abstract

Astronomical observations with gamma rays in the range of several hundred keV to hundreds of MeV currently represent the least explored energy range. To address this so-called MeV gap, we designed and built a prototype CsI:Tl calorimeter instrument using a commercial off-the-shelf (COTS) SiPMs and front-ends which may serve as a subsystem for a larger gamma-ray mission concept. During development, we observed significant non-linearity in the energy response. Additionally, using the COTS readout, the calorimeter could not cover the four orders of magnitude in energy range required for the telescope. We, therefore, developed dual-gain silicon photomultiplier (SiPM) boards that make use of two SiPM species that are read out separately to increase the dynamic energy range of the readout. In this work, we investigate the SiPM's response with regards to active area ($3\times3 \ \mathrm{mm}^2$ and $1 \times 1 \ \mathrm{mm}^2$) and various microcell sizes ($10$, $20$, and $35 \ \mu \mathrm{m}$). We read out $3\times3\times6 \ \mathrm{cm}^3$ CsI:Tl chunks using dual-gain SiPMs that utilize $35 \ \mu \mathrm{m}$ microcells for both SiPM species and demonstrate the concept when tested with high-energy gamma-ray and proton beams. We also studied the response of $17 \times 17 \times 100 \ \mathrm{mm}^3$ CsI bars to high-energy protons. With the COTS readout, we demonstrate a sensitivity to $60 \ \mathrm{MeV}$ protons with the two SiPM species overlapping at a range of around $2.5-30 \ \mathrm{MeV}$. This development aims to demonstrate the concept for future scintillator-based high-energy calorimeters with applications in gamma-ray astrophysics.