Critical-state flux-density profiles in type-II superconducting thin-film strips and disks
When a weak magnetic field is applied to a superconducting strip or disk of thickness d (of the order of the penetration depth {lambda}) much less than its width or radius, induced super-currents flow so as to prevent magnetic flux from penetrating the superconductor (except within {lambda} of the edge). A stronger field causes vortices to enter, and the profiles of the macroscopic flux density B are determined by critical-state equations describing bulk pinning. Near the sample edge, where the vortices are, the magnitude of the current density J is J{sub c}. In vortex-free regions of the sample, the magnitude of J is less than J{sub c} but is not zero. The profiles of B can be calculated analytically by assuming that J, averaged over the film thickness, is given by the difference between the values of the tangential component of B at the top and bottom surfaces of the film. This paper examines the basis for this assumption, which is equivalent to assuming that the current density is determined solely by the curvature of H, rather than by the gradient of its magnitude. It is shown that this is a good approximation for thin-film strips and disks.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames, IA (United States). Dept. of Physics and Astronomy
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 10149331
- Report Number(s):
- IS-M--780; CONF-940122--4; ON: DE94011199
- Country of Publication:
- United States
- Language:
- English
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