Monte-Carlo Simulations of Superconducting Tunnel Junction Quantum Sensors for the BeEST Experiment

The BeEST experiment uses Superconducting Tunnel Junction (STJ) quantum sensors to search for sterile neutrinos in the electron capture decay of Be-7. We are developing Monte-Carlo simulations to understand electron escape after the Be-7 decay and to distinguish between instrument artifacts and possible sterile neutrino signals. The goal of the simulation is to model the spatial trajectory of quasiparticles, phonons and the Li-7 daughter nucleus in the sensor. We will show preliminary results of the energy relaxation and the dependence of electron escape on the Be-7 implantation depth.