Results from the CsI Calorimeter onboard the 2023 ComPair Balloon Flight

TL;DR

This paper reports on the performance and observations of the CsI calorimeter onboard the 2023 ComPair balloon flight, demonstrating its technological readiness for future gamma-ray telescopes by analyzing background radiation and gamma-ray lines.

Contribution

First flight demonstration of the CsI calorimeter's capabilities in a balloon environment, validating its design for future gamma-ray observatories.

Findings

Observed background radiation and gamma-ray activation lines.

Measured the Regener-Pfotzer Maximum at high altitude.

Demonstrated the calorimeter's ability to detect high-energy events.

Abstract

The ComPair gamma-ray telescope is a technology demonstrator for a future gamma-ray telescope called the All-sky Medium Energy Gamma-ray Observatory (AMEGO). The instrument is composed of four subsystems, a double-sided silicon strip detector, a virtual Frisch grid CdZnTe calorimeter, a CsI:Tl based calorimeter, and an anti-coincidence detector (ACD). The CsI calorimeter's goal is to measure the position and energy deposited from high-energy events. To demonstrate the technological readiness, the calorimeter has flown onboard a NASA scientific balloon as part of the GRAPE-ComPair mission and accumulated around 3 hours of float time at an altitude of 40 km. During the flight, the CsI calorimeter observed background radiation, Regener-Pfotzer Maximum, and several gamma-ray activation lines originating from aluminum.