AN APPRECIATION OF QUASI-PARTICLE TRAPPING AND THE PROXIMITY EFFECT

Experimental results on X-ray detection with Nb-Al-AlOx-Al superconduc ting tunnel junctions are presented. For the first time, we can report that the spectra from devices without a proximity effect at the Nb-Al interface are remarkably similar to those that do have a proximity ef fect. The similarity is due to the response of the Al junction being d ominated by the detection of high energy phonons produced by the trapp ing, or recombination processes occurring in the Nb absorber after a p article interaction. These results indicate that the unequivocal demon stration of quasiparticle trapping requires a thorough understanding o f the phonon response in these types of detector.