Tunneling of nonequilibrium quasiparticles excited by x-ray quanta in a nonsymmetric superconducting tunnel detector

Pulse height distribution from nonsymmetric superconducting Nb/Al/AlOx/Nb tunnel junction irradiated by x-ray quanta emitted by a 55Fe source is studied. Signals of opposite polarity emerging as a result of absorption in different electrodes of the tunnel junction are observed at low bias voltages. This makes it possible to obtain amplitude spectra of essentially different shape for each electrode separately. The dependence of the maximum charge output on the bias voltage is analyzed. The diffusion coefficient, effective lifetime, and recombination probability for quasiparticles are obtained. It is found that the charge output increases with the magnetic field strength.