High resolution X-ray and infrared detectors using magnetic penetration depth thermometers

We are developing a high-resolution X-ray detector using a magnetic penetration depth thermometer (PDT). A PDT uses the strong temperature dependence of the magnetic penetration depth of a superconducting film. PDTs were originally developed for use at liquid helium temperatures and achieved resolutions on the order of 2 nK. The low intrinsic heat capacity and high sensitivity make it potentially useful for X-ray microcalorimetry. Using a superconducting bilayer film of aluminum and silver, a PDT can be developed to work at 100 mK or lower. A detector with a 1 mm pixel would be background limited and have an intrinsic resolution better than 2 eV out of 6 keV. Higher resolutions could be achieved for lower energy sources, making this technique useful as an infrared bolometer. Results of the current work will be presented along with analysis of design issues.