Non-equilibrium normal metal superconducting tunnel junction detectors

Measurements of a Normal metal-Insulating-Superconducting (NIS) tunnel junction sensor Ag/AlOx/Al coupled to a thick Pb absorber are presented. All films were thermally deposited on a Si3N4 membrane using a shadow-mask technique. Irradiation experiments with a Fe-55 source were performed using a high bandwidth SQUID with one junction only. We observe a strong position dependence of the pulse shape and amplitude. The different classes of events are probably related to different elements of the sensor. At a bath temperature of 80 mK we have obtained for the main Mn K-alpha peak an energy resolution of 100 eV FWHM. We have preliminary evidence for absorption in the lead and efficient trapping of the resulting quasiparticles on the NIS normal electrode.