Signal transmission by phonons and quasiparticles in a superconductor

The perturbation caused in a superconductor by a nuclear reaction such as ν+115In soon results in a volatile excited state of quasiparticles and of phonons having energies of the same order as the gap 2Δ ≅ 1 meV. The propagation of these two types of excitations was studied in detail in single-crystal tin, a superconductor material close to indium. A variety of waveforms are observed at the crystal boundaries, according to experimental conditions. The efficiency of several types of thin film transducers - bolometers and tunnel junctions is discussed. It is concluded that phonon-mediated signal transmission is a valuable alternative to quasiparticle transport and detection. (author) 7 refs.; 3 figs