Detection of X-rays using superconducting series-junction detectors

X-rays were measured using quantum superconducting series-junction detectors that consist of an Si substrate and four arrays of superconducting tunnel junctions on the substrate. The detectors are not calorimeters but quantum detectors even though they are making use of phonons; therefore, the detectors can be larger and faster than micro-calorimeters. Superconducting tunnel junctions with thinner tunnel barriers and a new arrangement contributed in obtaining higher energy resolutions than before. The full rise-time of signal outputs from charge-sensitive preamplifiers, i.e., charge collection time of the detector, was approximately 5 μs. A peak-to-background ratio of 8000 and an energy resolution of 70 eV were obtained for 5.9 keV X-rays. The energy resolution is about two times better than those of semiconductor detectors. These results suggest that the superconducting series-junction detectors can be practical high resolution detectors for X-rays.