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

Nb-based superconducting tunnel junctions (STJs) with Al trapping layers ha ve been developed for X-ray detectors. One applications for STJs is a low e nergy radiation detector having energy resolution and a high photon countin g 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, a nd f or 200 eV photon, It eV Full Width Half at Half Maximum (FWHM) with a 20 X 20 mu m(2) junction were achieved. In this article, the fabrication techniq ue and preliminary results of measuring the response for this band of energ ies are reported.