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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. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Analysis has been made of the amplitudes of the second and third harmonics when pumping a discrete frequency to the Josephson-vortex photonic crystal within the THz range of the electromagnetic spectrum. The results of numerical simulations show that there are certain resonance frequencies for these harmonics where the amplitudes are strongly enhanced. The frequencies at which these resonances occur can be tuned by an applied magnetic field and tilting the material with respect to the incident radiation. For the second harmonic it has been possible to describe these resonances analytically with a resonance approximation which displays good agreement with numerical simulations at and near the resonances. A similar perturbative method has been used to simulate the nonlinear mixing of two discrete THz frequencies in the JV photonic crystal, producing resonances for harmonics at the sum and the difference of these two input frequencies. This method can allow a high degree of control over the harmonic frequencies produced.

published_or_final_version / abstract / Physics / Master / Master of Philosophy

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