Improved Tantalum-based Superconducting Tunnel Junction Radiation Detectors for a Sterile Neutrino Search

Sterile keV neutrinos are natural extensions to the standard model of particle physics and a possible candidate for warm dark matter. STAR Cryoelectronics has developed radiation detectors that are currently used by a collaboration between the Lawrence Livermore National Laboratory (LLNL) and the Colorado School of Mines for the worldĺs most sensitive sterile neutrino search in the mass range from 100 to 850 keV. These quantum sensors are based on superconducting Ta/Al-AlOx-Al/Ta tunnel junctions (Ta-STJs) that have improved the exclusion limits for sterile neutrinos in the 100 keV mass range by more than an order of magnitude, but further sensitivity improvements are needed. General statement of how this problem is being addressed Recent experimental data have identified specific shortcomings of the existing detector designs and fabrication processes. We expect that the sensitivity can be enhanced by another order of magnitude with further optimization of the detector design and fabrication processes. Both will be addressed in Phase I to demonstrate and confirm feasibility. Work to be completed in Phase I We will optimize the detector designs and fabricate improved Ta-STJ detectors with enhanced sensitivity in Phase I. The improved Ta-STJ quantum sensors will then be tested at LLNL for use in a sterile neutrino search and for high-resolution X-ray spectroscopy. Commercial applications and other benefits The same type of tantalum quantum sensors can also be used in our companyĺs high-resolution X-ray spectrometers that we offer for X-ray microscopy and synchrotron science applications. The Ta-STJs will increase instrumental sensitivity for diverse applications such as particle contaminations on microchips, reaction mechanisms of metalloproteins and dopant chemistry in novel materials.