Development of a 1MJ cryocooler-cooled split magnet with Ag-sheathed Bi2223 tapes for Si single-crystal growth applications

A project to develop a high-temperature superconducting split magnet for Si single-crystal growth applications began iri October 1997 and is scheduled to be completed for three years. The project is being executed on the basi s of collaboration between Toshiba Corp., Sumitomo Electric Industries Ltd. and Shin-Etsu Handotai Co.,Ltd.; and is partially funded by Ministry of In ternational Trade and Industry (MITI) of Japan. The purpose of this project is to confirm the energy-saving performance and high reliability of a larg e HTS split magnet (1MJ) using Bi2223 tapes. This split coil system is comp osed of 2 coils, each consisting of 18 pancakes, and the total length of HT S tapes is approximately 80km. The magnet is to be cooled to below 20K by a highly efficient GM-type cryocooler in order to make overall current densi ty of the magnet close to the density of metal superconducting magnets. In the first year of this project, a conceptual design was established and R&D of the fragile HTS tapes was carried out. In the second year, the design, fabrication, testing and evaluation of an experimental magnet, incorporatin g pancake coils of the same size as those of the actual magnet, has been ac complished. This work will contribute to the improvement of the design and fabrication of the full-scale magnet in the final year of this project.