Avalanche effect in the planar array of superheated superconductors

Nucleation of the Supercooled Normal to Superconducting Phase Transition in Small Indium Spheres Induced byγRadiation

“…In fact, the a source flips granules an order of magnitude more efficiently than the g source. Note also that flips due to a particles have been observed in a previous experiment [6]. Thus one concludes that the a particles did not induce nucleation of the supercooled normal to superconducting transition, presumably because too much energy is deposited into a granule.…”

“…Our group fabricated a new SSG detector based on a planar array of superheated superconductors (PASS) produced by photolithography followed by melting in the presence of a wetting agent [4], and we have been investigating its potential for detecting dark matter, i.e., weakly interacting massive particles (WIMPs), neutrons, and neutrinos [5,6]. By appropriately adjusting the temperature T and applied magnetic field B 0 , the granules can be set in the superheated superconducting state very close to the line separating that phase with the normal one.…”

“…The flips and flops are read out as steps on the SQUID read-out and the actual magnitude of the signals depends on the particular experimental condition pertaining in the experiment (B 0 , geometry of pick-up coil, etc.). Normally, in the detecting mode [4][5][6], T and B 0 are set to be at the onset of the transition regime in which granules are beginning to flip (on increasing the temperature) from the superheated superconducting state to the normal state. For this experiment to test whether radiation can nucleate the superconductivity we set T and B 0 in the regime in which the granules flop (on decreasing T ) from the supercooled normal state to the superconducting state, and Fig.…”

Cryogenic particle detectors

“…This temperature spread T /T can be converted into a corresponding magnetic field spread of 6%, which is about an order of magnitude better than in the case of colloidal granule detectors [Leg90]. Arrays of granules were also produced in a microgravity experiment on a parabolic flight which, however, led only to a marginal improvement in the temperature spread T /T [Meg92].…”

“…The arrays were placed in an external magnetic field and the phase transitions read-out by a SQUID. In most of their experiments, the UBC group swept the temperature and kept the magnetic field constant, because the magnetic field sweep mode was practically impossible when using a SQUID [Meg92].…”