Aluminum STJ Development Towards Phase-IV of the BeEST Experiment*

The Beryllium Electron capture in Superconducting Tunnel junction (BeEST) experiment is a search for sub-MeV neutrino mass states in the electron capture decay of ⁷Be.  Phase-IV of the experiment requires the use of new Al-based STJ arrays to improve our sensitivity by more than two orders of magnitude.  The Phase-IV STJ sensors are purpose designed and fabricated for the BeEST experiment and include several key features that allow for higher precision measurements of the decay spectrum.  In this talk, I will present the basic design changes and the motivation for using Al-based sensors, as well as show data collected from our prototype aluminum devices with a comparison to data from our previous tantalum-based arrays.

LLNL-PRES-843745