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
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