Date: October 9, 2026

Time: 12:00 pm – 1:00 pm

Location: Sessler Conference Room – 50A-5132 [Hybrid and In-Person]

Speaker:  Stefan Freidrich (LLNL)

Title: Superconducting Tunnel Junctions and the BeEST Sterile Neutrino Search

Abstract: Superconducting tunnel junction (STJ) quantum sensors combine high energy resolution of low-temperature detectors with the high speed of athermal devices. We have developed tantalum-based STJ sensors that have an energy resolution of a few eV at energies below 1 keV and can be operated at rates about 1000 events/s. We currently use them at LLNL to search for hypothetical sterile neutrinos in the sub-MeV mass range with precision measurements of the electron capture decay of Be-7 implanted into the STJs. Upon decay, the neutrino escapes from the STJ detector, but the recoil of the Li-7 daughter nucleus can be measured very accurately to infer the neutrino mass. Heavy sterile neutrinos would reduce the recoil energy and produce additional peaks in the spectrum at lower energy. Our “Beryllium-7 Electron Capture in Superconducting Tunnel junctions” (“BeEST”) experiment currently provides the most stringent exclusion limits on the existence of heavy neutrinos in the mass range from 100 to 800 keV. The BeEST experiment is currently being scaled to small STJ arrays, and the search is being expanded to other BSM particles. This talk will introduce the basic physics of STJ quantum sensors and discuss the current status of the BeEST sterile neutrino search.

Join Zoom Meeting
https://lbnl.zoom.us/j/95016696011?pwd=Tk1XOW1Xd3RYRnlsc2tEYmRWZlVVZz09

Meeting ID: 950 1669 6011

Passcode: 247722