Publication Date

1994

Document Type

Dissertation/Thesis

First Advisor

Crabtree, George (Physicist)

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Physics

LCSH

Vortex-motion; Imaging systems; High temperature superconductors; Magnetic flux; Magnetooptical devices

Abstract

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.

Comments

Includes bibliographical references (pages [77]-80)

Extent

vii, 80 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

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.

Media Type

Text

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