| The purpose of this thesis was to investigate the propagation of fluxons on long Josephson junctions having spatial variations in the London penetration depth of the superconducting junction electrodes. The fundamental behavior of the fluxons on these types of junctions was modeled analytically and numerically, and this information was related back to the current voltage characteristics of the junction. These results were then corroborated experimentally.;Theoretically, a perturbation theory based on a simple linear expansion about the single soliton solution was used to examine the effect of sharp, step-wise variations of the London penetration depth on the soliton motion. In the process of doing this, a formal connection between this perturbative technique and one outlined by D. W. McLaughlin and A. C. Scott;The experimental investigation into this problem verified the theoretical results in the limit where the soliton velocity approached the speed of light on the junction. The actual devices were constructed using a niobium nitride - lead technology, which required extensive investigation into the properties of D.C. magnetron reactively sputtered niobium nitride thin films. As part of this effort, a study of the nitridization of niobium cathodes was undertaken, which made it possible to correlate the properties of superconducting niobium nitride films with the structure and composition of the surface of the sputtering target. |
