Next Generation Ta-STJ Sensor Arrays for BSM Physics Searches
Abstract
The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) experiment uses superconducting tunnel junction (STJ) sensors to search for physics beyond the standard model (BSM) with recoil spectroscopy of the Be EC decay into Li. A pulsed UV laser is used to calibrate the STJs throughout the experiment with 20 meV precision. Phase-III of the BeEST experiment revealed a systematic calibration discrepancy between STJs. We found these artifacts to be caused by resistive crosstalk and by intensity variations of the calibration laser. For phase-IV of the BeEST experiment, we have removed the crosstalk by designing the STJ array so that each pixel has its own ground wire. We now also use a more stable UV laser for calibration. The new STJ arrays were fabricated at STAR Cryoelectronics and tested at LLNL and FRIB. They have the same high energy resolution of 1-2~eV in the energy range of interest below 100~eV as before, and they no longer exhibit the earlier calibration artifacts. We discuss the design changes and the STJ array performance for the next phase of the BeEST experiment.
Keywords
Cite
@article{arxiv.2510.03556,
title = {Next Generation Ta-STJ Sensor Arrays for BSM Physics Searches},
author = {Joseph P. T. Templet and Spencer Fretwell and Andrew Marino and Robin Cantor and Ad Hall and Connor Bray and Caitlyn Stone-Whitehead and Inwook Kim and Francisco Ponce and Wouter Van De Pontseele and Kyle G. Leach and Stephan Friedrich},
journal= {arXiv preprint arXiv:2510.03556},
year = {2026}
}
Comments
5 pages, including references; 8 Captioned figures, though 14 total .png files displayed; Pre-print of Conference Proceedings for the 21st LTD conference; Submitted to IEEE TASC