Crabtree, George (Physicist)
M.S. (Master of Science)
Department of Physics
Vortex-motion; Imaging systems; High temperature superconductors; Magnetic flux; Magnetooptical devices
The production of useful devices from high temperature superconductors relies on the creation of microstructural defects which pin vortices, thereby preserving the ability of a type II superconductor to carry a lossless current. Until recently, the effect of different types of defects on pinning vortices has been mainly studied by methods which determine the average response of a sample. These techniques are by definition insensitive to the local pinning and de-pinning events which are of interest. This thesis addresses the subject of determining the local pinning properties of a defect. A magnetooptical technique will be utilized for observing the motion of magnetic flux lines in a superconductor, thus allowing a characterization of the local pinning properties of different defects. In particular, the design and construction of a miniature gas-flow cryostat will be described. Next, this cryostat is utilized in conjunction with a polarized light microscope for characterizing the pinning properties of twin boundaries in the Y 1B2C3O7.5 superconductor. Twin boundaries are found to exhibit anisotropic critical currents which are both temperature and field dependent.
Gardiner, Thomas A., "Development of a magneto-optical flux imaging system for studies of vortex dynamics in high Tc superconductors" (1994). Graduate Research Theses & Dissertations. 2167.
vii, 80 pages
Northern Illinois University
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.