Development of superconducting tunnel junctions for ultra soft X-ray detectors

Nb-based superconducting tunnel junctions (STJs) with Al trapping layers have been developed for X-ray detectors. One applications for STJs is a low energy radiation detector having energy resolution and a high photon counting rate. STJs have good potential in the band of energies from 40 eV up to 1 keV, because STJs materials have good absorbing properties in this region. The energy resolution was measured by using the Photon Factory beamline BL-12A of High Energy Accelerator Research Organization (KEK) in Japan, and for 200 eV photon, 11 eV Full Width Half at Half Maximum (FWHM) with a 20/spl times/20 /spl mu/m/sup 2/ junction were achieved. In this article, the fabrication technique and preliminary results of measuring the response for this band of energies are reported.