Development of large arrays of microcalorimeters for precision gamma-ray spectroscopy

We present measurements from a gamma-ray microcalorimeter with a FWHM energy resolution of 42 eV at 103 keV on a gadolinium test source and 52 eV FWHM at 103 keV on a complex mixture of plutonium isotopes. Additionally, we provide an overview of microcalorimeter technology, its specialized readout electronics, and the associated cryogenics. NIST is presently developing arrays of microcalorimeters and microbolometers for applications at submillimeter and X-ray wavelengths. The largest of these arrays will have 10,240 pixels and a sensing area of 102.4 cm
²
. This technology development is directly applicable to gamma-ray microcalorimeter arrays and we see no obstacles to gamma-ray microcalorimeter arrays of 100 or more pixels