Quasiparticle diffusion over several mm in cryogenic detectors

The use of quasiparticle diffusion in a superconducting film has the potent ial to allow an increase in the size of a cryogenic detector without propor tional loss of energy resolution. The quasiparticle lifetime and the diffus ion constant are critical parameters which have limited this development. U sing W superconducting phase transition thermometers as the sensors and a W /Al bilayer as the diffusion film, we have measured quasiparticle diffusion over a distance of 2 mm and deduced a diffusion constant of D = 2.5 x 10(- 4) m(2)/s and a quasiparticle lifetime of tau = 9.0 Ins, which is, to our k nowledge, by far the longest ever observed. With Ir/Au thermometers and an Ir/Au/Al diffusion film we found D = 4.6 x 10(-3) m(2)/s and tau = 0.43 ms with diffusion over 4 mm, the longest distance observed to date. (C) 2001 E lsevier Science B.V. All rights reserved.