The equilibrium motion of vortices in two- and three-dimensional superconductors has been studied with a dc Superconducting QUantum Interference Device (SQUID). This technique has the advantage of probing the system in a non-invasive manner as well as providing dynamic information over many decades in frequency. Through measurements of the spectral density of magnetic flux noise, S[sub[Phi]]([omega]), as a function of temperature and applied magnetic field, the effects of proton and heavy ion irradiation on flux noise in crystals of YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] have been measured and compared with the effects on the critical current, J[sub c]. Both proton and heavy ion irradiation proved effective at reducing S[sub[Phi]]([omega]), with proton irradiation having a larger effect. Measurement of S[sub[Phi]]([omega]) due to the equilibrium Kosterlitz-Thouless-Berezinskii transition in two-dimensional Josephson Junction Arrays (JJAs) was studied as a function of temperature for three different arrays and using three different sensors. S[sub[Phi]] is shown to obey dynamic scaling over as many as five decades in frequency, and estimates are made for the dynamic critical exponent z. An analytic theory for the high- and low-frequency behavior of S[sub[Phi]]([omega]) is presented and compared to the measured data, with the result that the low-frequency behavior is well described by the theory but the high-frequency behavior is not. Other theories and numerical simulations are described and compared with the data, but none are completely satisfactory. Lastly, suggestions for necessary further theoretical work and possible future experimental work are suggested.

We have studied the behavior of fluctuation effects in superconducting systems using numerical simulations of XY and Coulomb gas models. Flux flow resistance in two dimensional Josephson junction arrays has been calculated, and related to correlations in vortex structure. Randomness has been introduced, and its effects on the superconducting transition, and vortex mobility, have been studied. We find that randomness destroys phase coherence, yet the randomness induced pinning reduces flux flow resistance at low temperatures. Vortex line fluctuations in high temperature superconductors have been studied using a three dimensional XY model. We have considered the melting of the vortex line lattice, and the entanglement and cutting of vortex lines in the vortex line liquid phase. Vortex line entangling and cutting appear to occur on the same length scales in the liquid phase. The vortex structure function has been calculated and from it, elastic properties of the vortex line liquid have been inferred. The two dimensional classical Coulomb gas, where charges map onto vortices in the superconducting system, has been simulated. The melting transitions of ordered charge (vortex) lattices have been studied, and we find evidence that these transitions do not have the critical behavior expected from standard symmetry analysis.

A wide range of progress in materials development [single crystals, ceramics, thin films, wire and tapes] is reported in the 169 papers in this volume. The main focus of the papers is in attaining a better understanding of the relationship between microstructure and electrical properties. Invited papers cover topics such as the effects of substitution and doping; multilayers; nanostructure characterisation; electric field effects in High Tc Superconductors [HTS]; surface stability; critical currents; flux pinning and magnetooptic imaging of flux patterns; effects of irradiation induced defects; properties and preparation of materials; microwave properties and electronic devices. A clearly broadened basis for understanding processes and mechanisms in [HTS] is portrayed. Appreciable progress has been achieved in the reproducible manufacturing of high quality materials supported by very efficient methods in microstructural analysis. This essential improvement is reflected in the increased number of practical devices encouraging the use of HTS in applications for electronics and power engineering, all of which are reviewed in depth in this work.