UBC Theses and Dissertations
Investigation of a superheated superconducting colloid Da Silva, Angela Jane
In recent years, there has been increasing interest in the idea of using a superheated superconducting colloid (SSC) as a detector for neutrinos and dark matter candidates. The primary objective of this work has been to investigate the basic properties of an SSC, consisting of 7 μm radius tin grains imbedded in epoxy, using a pumped ⁴He cryostat with a low vibrational noise RF-SＱUID readout system. The superheating-supercooling hysteresis curves of the colloid have been measured in applied magnetic fields ranging from 3.1 x 10⁻⁴T to 1.4 x 10⁻²T. The superconducting to normal phase transition in individual grains inside the colloid has been observed and the measured signal size is in reasonable agreement with the calculated values. Finally, it was demonstrated that the colloid could withstand up to 20Mrad of [omitted]-radiation without incurring a significant change in its superconducting-normal phase transition. A new type of sample, consisting of a planar array of 1 μm thick metal squares deposited on a mylar substrate, was developed. Both indium and tin were used as a. fabrication material. The characteristics of such samples were investigated, again using the pumped ⁴He cryostat. The full Meissner effect was only observed for applied magnetic fields less than 5 x 10⁻⁵T. For higher applied fields, the samples behaved like type-[omitted] superconductors in the mixed state regime, exhibiting flux penetration and trapping.
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