Training of LBL-SSC model dipole magnets at 1.8 K

The authors present the 1.8K training behavior of SSC Magnets, several of which have reached a peak current of 9400 A; a central field of 9 Tesla. For the SSC Project, more than 30 one meter long dipole magnets have been built and tested. The test results for the 4.3K operation have been presented previously. Magnet operation, primarily reaching design field without premature training, is expected to be superior in superfluid helium at 1.8K as compared with helium I at 4.3K. Not only is the critical current increased at the lower temperature, but the heat transfer is much improved. LBL has had an operating helium II facility for nine years and the authors standard test sequence has been to check for training in helium I at 4.3K and then cool the system down to 1.8K and train the magnet to its new, high limit. Because the mechanical forces are much greater at the higher currents and fields achieved at the lower temperature, information has been obtained on the adequacy of the mechanical design. Even for those magnets in which training quenches occurred in the inner layer at 4.3K, many of the quenches at 1.8K occurred in the outer layer. 10 refs., 8 figs