Responses of Superheated Superconducting Tin Granules to α-Ray Irradiations in Various Energy

Abstract

By sampling spherical tin granules of diameter from 145 through 250 μm one by one, we studied responses of them in the superheated superconducting state to incident α particles of energies less than 4.7 MeV in a range of temperature from 2.25 to 3.00 K in magnetic fields. Line shapes of the signals obtained in the phase transition were found out to have a half-width of 4∼8 μs in time. The energy sensitivity of the specimens was ascertained to increase with decreasing temperature. The superheated state turns normal with an energy deposit two orders of magnitude less than that is required for the whole of a granule to be uniformly heated up. This means that heating ∼0.1% of the volume is enough to trigger the full penetration of an applied field into a hit granule. Our results offer elements indispensable for applying the breakdown of the Meissner effect to the detection of weakly-interacting particles.