Development of practical soft X-ray spectrometers.

Cryogenic soft X-ray imaging spectrometers are currently being developed fo r applications in the fields of astronomy and material sciences, In this pa per we present experiments on optimized single devices, which show measured energy resolutions of 4.6 eV, 8.1 eV and 20.5 eV at 525 eV, 1.5 keV and 6 keV respectively. These energy resolutions combined with a quantum efficien cy of more than 40 % in the energy range from 0.5 to 2 keV together with a count rate capability of 15 kHz demonstrate the overall good performance of single Superconducting Tunnel Junctions (STJs), Assembling these optimized single devices in a matrix read-out would provide the practical basis for a soft X-ray imaging spectrometer.