Superconducting Tunnel Junction Detectors for Analytical Sciences

Superconducting tunnel junction (STJ) detectors exhibit superior detection performance for photons and particles at a high spectroscopic resolution of ~ 10 eV, a short dead-time (decay time) of ~ μs, a high quantum efficiency of ~ 100%, and a low detection threshold energy of less than 1 eV, which cannot be achieved by conventional detectors. The outstanding detection performance originates from a small superconducting energy gap of ~ meV, which is three orders of magnitude smaller than ~ eV in semiconductors. This paper reports our recent progress in two applications of STJ detectors to fluorescence-yield X-ray absorption fine structure (XAFS) spectrometry for trace light elements in matrices and mass spectrometry (MS) for ions with the same mass/charge-number ratio (m/z) but different charge states and neutral fragments.