THE ROLE OF EPITAXY IN SUPERCONDUCTING TUNNEL JUNCTION DETECTORS

We have experimentally analysed the use of epitaxial and polycrystalli ne tantalum trapping layers in tunnel junction detectors, using epitax ial niobium based double tunnel junction devices. We have shown that t he trapping rate is enhanced by having a low mean-free-path in the Ta trap film and an epitaxial Nb absorber film. This effectively increase s the proportion of time spent by a quasiparticle in the trap film. Ph onon-quasiparticle scattering, which reduces the effective trapping ra te, has been observed