Development of Hard X-ray and Gamma-ray Detector With Transition Edge Sensor for Nuclear Materials Analysis

We have designed and fabricated a hard X-ray and gamma-ray TES spectrometer for nuclear materials analysis. A superconducting tin (Sn) absorber is coupled to the TES film by using a gold (Au) bump post to improve the thermal contact between the absorber and the TES. To obtain a sufficient detection efficiency at the high energy photons near 100 keV, an 8-pixel array of TES microcalorimeters were developed. In this new device, the epoxy glue which is used to connect the absorber and the gold bump post was well controlled and hence the slow component of the decay time constant was improved from 7.82 ms to 4.46 ms compared to our old device. The energy resolution was 131 eV FWHM at 59.5 keV gamma rays, which is better than the limit of HPGe detectors (400 eV FWHM at 60 keV).