Development of superconductor radiation detectors

Recent results in the development of superconductor radiation detectors using superconducting tunnel junctions applied in the energy measurement of X-rays and the detection of heavy ions are reviewed. The energy resolutions of 41 eV, 58 eV, 65 eV, and 129 eV were obtained for 5.9 keV X-rays with 20 20 m, 100 100 m, 200 200 m, and 500 500 m STJs fabricated by introducing a plasma oxidization technique for the suppression of leakage current across the tunneling barrier. The performance in X-ray detection is being improved by the study of phonon-mediated X-ray signals for increasing X-ray detection efficiency and by installing a SQUID signal amplifier for suppression of the signal transmission loss and the electric noise. Direct voltage switching of STJ induced by heavy ions was successfully observed, which opens a new possibility to realize a radiation hard heavy ion detector with the timing characteristics of the order of picosecond.