Testing of the world's largest HTS experimental magnet with Ag-sheathed Bi-2223 tapes for Si single crystal growth applications

Funded by the Ministry of International Trade and Industry (MITI) of Japan, a project to develop a cryocooler-cooled high-temperature superconducting (HTS) magnet for Si single crystal growth applications began in October 1997 on the basis of collaboration between Toshiba Corp., Sumitomo Electric Industries Ltd, and Shin-Etsu Handotai Co., Ltd. So far, we have finished a design of the HTS magnet and basic tests using a model coil. The target magnet is composed of 36 single pancake coils using Ag-sheathed Bi2223 tapes and total length of the HTS tapes is approximately 80 km. Stored electromagnetic energy of the magnet will amount to 1 MJ at rated current operations. The magnet is to be cooled to below 20 K by a GM (Gifford-McMahon) cryocooler. Before fabricating the target magnet, we tested a model coil composed of 4 single pancake coils which were the same size as those of the target magnet, in order to investigate basic characteristics of the HTS coils. We performed a 290 A continuous current flowing operation using the model coil and reached 50 kJ of electromagnetic energy storage.