NIST microcalorimeter arrays for the hard x-ray and γ-ray astronomy

NIST has developed microwave multiplexed microcalorimeter arrays for the detection of hard X-rays andγ-rays (Bennett et al. 2012, Mates et al. 2017). The arrays are made of tin or bismuth absorbers that are read-out with arrays of Transition Edge Sensors (TES). Each TES is coupled via a SQUID to a microwave resonator, and a single microwave line is used to sample the response of the resonators of all pixels. The detector arrays achieve an energy resolution of 55 eV FWHM at 97 keV. We report here on the performance of a 34-pixels prototype TES with a collimated 50μm diameter 20-50 keV X-ray beam as well as a Eu(152) source for a future balloon flight. We will furthermore describe a planned stratospheric balloon flight that will be used to demonstrate the performance of a novel mini-dilution refrigerator and the 34-pixels prototype detector in a space environment.