Development of superconducting tunnel junction detectors for high-resolution X-ray spectroscopy

The energy resolution of aluminum superconducting tunnel junctions (Al-STJs) has been improved by the introduction of a metallic buffer layer underneath the junction. When irradiated by 5.9 keV X-rays, a resolution of 12 eV (FWHM) was achieved for a junction size of 100 x 100 mu m(2). A mobile refrigerator system allowed to characterize these devices at the PTB-beamlines of the electron storage rings Bessy I and Bessy II. They showed linear energy response in the range between 200 eV and 6.5 keV and a strong increase in reduced energy events if irradiated at X-ray energies below the Al absorption edge at 1.56 keV. (C) 2000 Elsevier Science B.V. All rights reserved.