Low-energy response of superconducting tunnel junction X-ray spectrometers

Niobium thin films coupled to aluminum layers that serve as quasiparticle traps in an Nb/A1/A12O3/A1/Nb tunnel junction X-ray detector are configured as low-energy X-ray spectrometers. Although the device is only moderately successful as an X-ray detector, it can nevertheless be used as the basis for larger, more efficient superconducting absorbers. Results indicate the feasibility of using a large range of energy as a diagnostic technique for superconducting tunnel junction x-ray detectors.