AC Magnetic Flux Profile and Critical Current Density Obtained by Campbell's Method in Polycrystalline MgB2

作者：Ni, Baorong^*; Morita, Yoshihiro; Liu, Zhiyong; Liu, Cuifang; Himeki, Keizo; Otabe, Edmund Soji; Kiuchi, Masaru; Matsushita, Teruo

来源：IEEE Transactions on Applied Superconductivity, 2009, 19(3): 3529-3532.

DOI：10.1109/TASC.2009.2019553

• AC flux profile
• Campbell's method
• grain connectivity
• polycrystalline MgB2 bulk

In this study, we focused on the estimation of the global critical current density, super-current path, grain connectivity and their relationships with the faults volume fraction in the MgB2 bulks prepared by a modified PIT (powder in tube) method. Campbell's method was applied for the purpose of acquiring the penetrating AC magnetic flux profile and the characteristic of AC magnetic field vs. penetration depth from the specimen's surface. A computer simulation on the penetrating AC flux profile in MgB2 bulks with certain amount of randomly distributed voids, oxidized grains and other faults was also carried out. The global critical current density obtained by Campbell's method turned out to be smaller than that obtained from the SQUID measurement, implying that the global super-current was reduced by the existence of various kinds of faults and the lack of the electrical connectivity between grains. It was verified that the relationship between the global critical current characteristics and the faults contained in MgB2 specimens can be quantitatively clarified by comparing the simulated critical current densities and other factors with the experimental results.

• 出版日期2009-6
• 单位桂林理工大学