Recent Progress from the BeEST Neutrino Experiment

The Beryllium Electron-capture in Superconducting Tunnel junctions (BeEST) experiment precisely measures the decay products of ⁷Be following nuclear electron capture (EC) to search for heavy neutrino mass states using superconducting quantum sensors. Following up the first limits from the Phase-II data reported last year [PRL 126, 021803 (2021)] using a single detector pixel counting for a month, we have started work on Phase-III to scale the experiment to multi-pixel arrays of sensors. In this talk I will present our progress towards increasing the sensitivity of the experiment by understanding the systematics associated with secondary particles from the decay (Auger and shaking electrons), materials effects, and sensor development for scaling to 32- and 128-pixel arrays.