High Resolution Alpha Particle Spectroscopy with Cryogenic Microcalorimeters

We present measurements from a novel cryogenic microcalorimeter designed to detect alpha particles. We demonstrate a spectral resolution of 4.4 keV FWHM for 5.3 MeV alpha particles from a
²¹⁰
Po source. In addition, we present an alpha spectrum from a mixture of Pu isotopes demonstrating the feasibility of resolving the individual contributions of
²³⁹
Pu and
²⁴⁰
Pu. The unmatched resolution of microcalorimeter alpha detectors will provide new capabilities for actinide analysis. We discuss potential applications and also sensor design.