ComPair: A Next Generation Medium Energy Gamma-ray Telescope Prototype

The Compton Pair (ComPair) project aims to develop the necessary technologies for future medium energy gamma-ray missions that can address many questions posed in the recent Astro2020 Decadal survey in both the New Messengers and New Physics and the Cosmic Ecosystems themes. Over the past few years, the ComPair team has built a balloon payload that consists of 4 detector subsystems that together detect and characterize photons via Compton scattering and pair production, enable a veto of cosmic rays, and are a proof-of-concept for a space telescope with the same architecture. The original ComPair instrument had a successful 5 hour engineering flight from Fort Sumner, New Mexico in August 2023. The team now is working to upgrade the ComPair instrument by incorporating novel silicon pixel detectors, to enable a lower-noise and improved particle tracking sensitivity, in addition to other design optimizations from the AMEGO-X MIDEX mission concept. With a significant increase in the detector active area, the next version of ComPair (ComPair-2) will have an order of magnitude improvement in sensitivity over the original balloon payload. Furthermore, the ComPair-2 instrument will be used as a test-bed for MeV mission software with improved machine learning event identification techniques in the Compton and pair regime. In this presentation we will give an overview of the ComPair project, recent results from the inaugural balloon flight, and the on-going development of the upgraded ComPair-2 instrument.