Particle detection with superheated superconducting grains

Electrons having kinetic energy of the order of a few hundred keV can induce superconducting-to-normal transitions in an assembly of metallic spheres in a superheated state. We study this phenomenon in several type I superconductors (In, Hg, Sn, and Sn–Pb alloy) at different electron energies. Experiments show that the transition cross section is strongly dependent upon grain size and thermal properties of the superconductor. We develop a phenomenological model which qualitatively describes the above features, as well as the field and temperature dependence of the transition probability. Possible application to particle detection, particularly of low-energy charged particles and heavy ions, are discussed.