Magnetic Field Dependence of Critical Current Density of Polycrystalline Tl-2223 Wire

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Abstract
The magnetic field dependence of critical current density J c for polycrystalline Tl-2223 tape-shaped wire was examined in terms of a model regarding a sample as a bulk which consists of an anisotropic superconductor with an incomplete crystal alignment. We assumed that the critical current density in each grain would be governed only by the perpendicular component of magnetic field to the a-b plane, especially in a high magnetic field. In a low field, we also assumed that the grain boundary weak link would be dominant in terms of J c. It was found that the magnetic field dependency of J c in high fields was well described by the present calculation in spite of an inconsistency in low magnetic fields. It was predicted that a practical J c value of more than 10,000 A/cm2 in a magnetic field above 5T might be possible with a crystal alignment factor of standard deviation σ below 0.5, assuming the crystal alignment in the wire to be of Gaussian distribution.