Progress towards a wideband x-ray focal plane using kinetic inductance phonon mediated detectors

Kinetic-inductance phonon-mediated detectors (KIPMs) are a class of sensors that exploit phonon-to-quasiparticle generation in thin-film superconductors to finely resolve incident energy deposits within a crystalline substrate. Due to their high multiplexability, ability to couple to thick absorbers, and relatively simple design scheme, these devices have the potential to realize a broadband 0.1-200 keV x-ray photon detector with O(1-10) eV resolution. A simple focal plane with 1000s of such KIPMs would make this concept well suited for future space missions. We present experimental measurements of a preliminary design, fabricated using O(1) mm aluminum pixels on a mm-thick silicon wafer, and exposed to an Fe-55 source, indicating good agreement with the expected O(100) eV resolution for this un-optimized variant. We will also outline an optimized design, using 450 um x 450 um α-Tantalum pixels as the thin-film absorber, potentially allowing us to reach our goal energy and spatial resolutions.