Pulse height distribution from nonsymmetric superconductingNb/Al/AlOx/Nbtunnel junction irradiated by x-ray quanta emitted by a55Fesource 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. ©1997 American Institute of Physics.