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arXiv · 2503.02493

Bottom-up Background Simulations of the 2016 COSI Balloon Flight

Savitri Gallego·Uwe Oberlack·Jan Lommler·Christopher M. Karwin·Andreas Zoglauer·Pierre Jean·Peter von Ballmoos·Carolyn Kierans·Clio Sleator·John A. Tomsick·Steven E. Boggs
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Abstract

The Compton Spectrometer and Imager (COSI) is a Compton telescope designed to survey the 0.2-5 MeV sky, consisting of a compact array of cross-strip germanium detectors. As part of its development, in 2016 COSI had a successful 46 day flight on board NASA's Super Pressure Balloon platform. This was a precursor to the COSI Small Explorer (COSI-SMEX) satellite mission that will launch in 2027 into a equatorial low Earth (530 km) orbit. The observation of MeV gamma-rays is dominated by background radiation, especially due to the activation of the detector materials induced by cosmic-ray interactions. Thus, background simulation and identification are crucial for the data analysis. Because the COSI-SMEX detectors will be similar to the ones used for the balloon flight, the balloon measurements provide an important tool for testing and cross-checking our background simulations for the upcoming space mission. In this work we perform Monte Carlo simulations of the background emission from the 2016 COSI balloon flight. Including a phenomenological shape correction, we obtain an agreement with the data at the 10-20% level for energies between 0.1-1.6 MeV, and we successfully reproduce most of the activation lines induced by cosmic ray interactions.

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Savitri Gallego, Uwe Oberlack, Jan Lommler, Christopher M. Karwin, Andreas Zoglauer, Pierre Jean, Peter von Ballmoos, Carolyn Kierans, Clio Sleator, John A. Tomsick, Steven E. Boggs. 2025-03-04. Bottom-up Background Simulations of the 2016 COSI Balloon Flight. https://doi.org/10.3847/1538-4357/add6a0

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