Improved electronics for BeEST sterile neutrino search

The BeEST experiment is probing for “Beyond the Standard Model” (BSM) physics in the form of , massive sterile neutrinos possibly ejected in the electron capture decay of 7Be to 7Li from 7Be ions implanted in Ta Superconducting Tunnel Junctions (STJs), where a sterile neutrino would produce a different 7Li ion's recoil energy. Provided with suitable electronics, STJs can measure energy with an accuracy of 1-2eV. Existing electronics not only produce excess nois but can no longer be manufactured due to parts obsolescence. Per BeEST requirements, the next-generation STJ array electronics should have noise levels reduced by a factor of 10 or more, full trace capture capability and coincidence timing at the 100ns level. We will approach this problem by first redesigning the preamplifier with modern parts to improve resolution and lower power and then apply our experience building standard NP DAQ systems to develop a system optimized for the specific requirements of STJ detectors. In Phase I we screened ultra-low noise FET transistors to locate one with half the noise, designed and built a new circuit that could connect it to an STJ detector and cut power by over four times and used careful noise measurements to make circuit adjustments and signal processing changes to reduce overall noise by factors up to 30. In Phase II we will turn the successful preamplifier circuit into a 32 channel preamplifier card and develop the other components that comprise a modern nuclear data acquisition (DAQ) system including precision digital-to-analog converter card, preamplifier digital control card, and a central computer on a module that can stream captured signal traces to a host computer at 1000/sec/STJ. The most important benefit of a successful project will be the availability of a new measurement tool for Nuclear Physics, since STJ Array detectors are excellent at accurately measuring all types of nuclear reaction product at very low energies, as the SALER instrument is demonstrating at FRIB. As BeEST shows, these detectors also enable cutting edge science by small research groups, which will create improved R&D opportunities in the nuclear sciences and allow universities to train the next generation of Nuclear Physicists in quantum measurement techniques. Finally, sales of complete instruments of simply the DAQ systems will enhance our local economy and improve the nation's balance of trade through overseas sales.