Training of LBL-SSC model dipole magnets at 1.8 K

The 1.8 K training behavior of SSC (Superconducting Supercollider) magnets, several of which have reached a peak current of 9400 A is presented. For the SSC Project, more than 30 one-meter-long dipole magnets have been built and tested. Magnet operation, primarily reaching design field without premature training, is expected to be superior in superfluid helium at 1.8 K as compared with helium at 4.3 K. Not only is the critical current increased at the lower temperature, but the heat transfer is much improved. LBL (Lawrence Berkeley Laboratory) has had an operating helium II facility for nine years and the standard test sequence has been to check for training in helium I at 4.3 K and then cool the system down to 1.8 K 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 on the adequacy of the mechanical design has been obtained. Even for those magnets in which training quenches occurred in the inner layer at 4.3 K, many of the quenches at 1.8 K occurred in the outer layer