Quasiparticle and phonon propagation in superheated superconducting granules after nuclear recoils

The propagation of the excess of quasiparticles and phonons produced by a nuclear recoil inside Sn and Zn superheated superconducting granules will be discussed. The decay towards equilibrium of the initial disturbance is assumed to be a thermal diffusion process described by a set of coupled heat flow equations for the effective quasiparticle and phonon temperatures. The solution is carried out analytically for a point source located anywhere inside the superconducting granule with the initial energy distributed in both quasiparticle and phonon systems. The calculated time delay between the neutron interaction and the nucleation of the phase transition will be compared to the time delay distributions obtained by irradiating Zn and Sn SSG detectors with a 70Me$\!$V neutron beam.