Monte Carlo Modeling of sub-keV Backgrounds in Superconducting Tunnel Junctions from Gamma-Ray Interactions for SALER@FRIB

The new Superconducting Array for Low-Energy Radiation (SALER) experiment at FRIB aims to directly embed short-lived isotopes in superconducting tunnel junction (STJ) sensors to measure nuclear recoil energies from weak decay as a search for BSM physics. At these eV-scale energies, small energy depositions from simultaneous higher-energy events (since as gamma rays) generate backgrounds which are important to understand. In this talk, I will present the first Monte Carlo modeling using the test case of 137Cs decays where a 662 keV gamma-ray is emitted and deposits small energies in the silicon substrate of the STJ as a critical first step towards background characterization for SALER@FRIB.