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

TL;DR

This paper develops Monte-Carlo simulations of superconducting tunnel junction sensors to improve understanding of their response in sterile neutrino searches, aiding signal interpretation.

Contribution

It introduces spatially-resolved Monte-Carlo simulations of energy relaxation in superconductors for STJs used in sterile neutrino detection.

Findings

Simulation results agree with literature values for charge generation and Fano factor.

Initial simulations match observed escape tail features.

Fine structure in line shape observed in simulations will be refined with better data.

Abstract

Superconducting Tunnel Junctions (STJs) are used as high-resolution quantum sensors to search for evidence of sterile neutrinos in the electron capture decay of $^7$Be. We are developing spatially-resolved Monte-Carlo simulations of the energy relaxation in superconductors to understand electron escape after the $^7$Be decay and distinguish details in the STJ response function from a possible sterile neutrino signal. Simulations of the charge generation and the Fano factor for different materials agree with the literature values. Initial simulations of the escape tail are consistent with observations, and contain fine structure in the line shape. The line shape will be refined as better experimental data become available.