Niobium-copper superconductor-normal metal-superconductor asymmetry modulated SQUIDs

We have developed a fabrication method using a focused ion beam microscope that allows us to produce SNS junctions in which thermally energetic electrons can enter the N region. We report on SQUIDs made with this technique which we are developing as proof of concept devices and prototype high energy resolution spectrometers. We discuss the various design parameters used for our devices and present results from our prototype SQUIDs. We present results for devices with a variety of N-electrode structures and discuss their suitability for our application.