Influence of Wall Thickness on Magnetic Shielding Effects of BPSCCO Cylinders
The critical current density (J c ) of high critical temperature (T c ) superconductor is an important parameter in magnetic shielding. However, it is difficult to fabricate very high-J c material. The present research group has been improving magnetic shielding effects for high-T c , superconducting cylinders by using special techniques. As one of the basic research areas for the improvement of magnetic shielding effects and the fabrication of large sized cylinders, the present paper analyzes the relationship between the wall thickness (w) of the cylinder and the maximum magnetic shielded field (B s ) by use of critical state models. The values of B s are systematically measured by changing the w values of BPSCCO cylinders at a temperature of 77.4 K. It is found that the values of B s do not change linearly with the values of w, and the theoretical values of B s agree well with the experimental values. The temporal change of the maximum magnetic trapped field (B t ) is also analyzed by Anderson-Kim flux-creep theory, with the experimental results of the temporal change of B t agreeing well the theoretical results. It is observed the periodic dependence of DC-SQUID voltage on the applied magnetic field in the center of the superconducting cylinder.
KeywordsApplied Magnetic Field Critical Current Density Effective Shield Critical State Model Cold Isostatic Press
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- 1.J. P. Wikswo, and M. C. Leifer, Superconducting Magnetometry for Biomagnetic Measurements, “Near Zero: New Frontiers of Physics”, J. D. Fairbank, B. S. Deaver, C.M. F. Evenritt, and P. F. Michelson, ed., W. H. Freeman and Company, New York, 456 (1988).Google Scholar
- 3.B. Cabrera, Near Zero magnetic Fields with Superconducting Shields, “Near Zero: New Frontiers of Physics“, J. D. Fairbank, B. S. Deaver, C.M. F. Evenritt, and P. F. Michelson, ed., W. H. Freeman and Company, New York, 312 (1988).Google Scholar
- 5.M. Itoh, Applications of High T c Superconductor to Magnetic Shielding, OYO BUTSURI (J. Jpn. Soci. Appl. Phys.) 60: 478 (1991).Google Scholar
- 6.M. Itoh, Magnetic Shielding by High-Tc Superconductors: Shielding Effects of YBCO Cylinders, “Advances in High-Tc Superconductivity“, D. Andreone, R. S. Connelli, and E. Mezzetti, ed., World Scientific, Singapore, 232 (1992).Google Scholar
- 13.T. Ohyama, M. Itoh, T. Minemoto, and K. Hoshino, Improvement in Magnetic Shielding by use of a Triple-Cylinder Configuration of Superconducting BPSCCO, Advances in Cryogenic Engineering-Materials 40: (1994), to be publish.Google Scholar
- 16.M. Tinkham, “Introduction to Superconductivity”, MacGraw-Hill Inc., New York, 1975.Google Scholar