Diffusion of long-lived quasiparticles over long distances

Diffusion of quasiparticles over distances up to 4 mm has been observed in various superconducting films. The quasiparticles were created by X-ray abs orption in film strips with critical temperatures near 1 K and were detecte d in two superconducting phase transition thermometers at the ends of each strip. Position and energy of the absorbed X-rays as well as diffusion cons tants and lifetimes of the quasiparticles were determined. Very long lifeti mes up to 9 ms allow the realization of large area phonon collector films o n massive cryogenic particle detectors. Recently, with a first such detecto r a high efficiency of the phonon collection could be demonstrated. (C) 200 0 Elsevier Science B.V. All rights reserved.