PULSED-FIELD MAGNETIZATION APPLIED TO HIGH-T-C SUPERCONDUCTORS

The pulsed-field magnetization (PFM) technique has been elaborated as the most efficient and effective tool in magnetizing the melt-processe d high-T-c bulk superconductor in the temperature range 30-80 K. The d ynamic motion of magnetic fluxes penetrating into the YBCO superconduc tor during the PFM operation has been analyzed and the flux propagatio n speed has been accurately evaluated. The viscous force is found to p lay a very crucial role in the PFM process. Detailed analysis of the f lux motion in the presence of both viscous and pinning forces enabled us to find a very efficient method for magnetization by the PFM operat ion. The iteratively magnetizing pulsed field operation with reducing amplitudes abbreviated as 'IMRA' has been developed and proved to be v ery effective in magnetizing high-T-c superconductors at temperatures as low as 30 K. By making full use of these findings, we constructed a prototype quasi-permanent magnet system capable of producing magnetic field of 0.8 T in the outerspace at 7 mm above the surface of the mag netized YBCO superconductor. (C) 1998 Elsevier Science Ltd. All rights reserved.