Development of high current vapor-cooled current leads for large superconductor critical current measuring

Several programs to develop superconducting magnets for the Large Helical Device (LHD) are under way at the National Institute for Fusion Science in Japan. The development of large-scale superconductors for use in superconducting magnets is an important goal of these programs. To measure the critical current of such large-scale superconductors it is necessary to supply a very high current of up to 100 kA. For this purpose, very large current capacity, vapor-cooled current leads have been developed. As a first step in this development, a pair of current leads with a short-time rated current of 30 kA has been made and tested. Also developed was an analytical program to calculate the time-dependent characteristics of vapor-cooled current leads, and the results of calculations with the experimental results obtained with 30 kA current leads were compare