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 1keV, 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 for 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 technique and preliminary results of measuring the response for this band of energies are reported.