Recent status of SSC magnets

Eighteen 5cm aperture, 15m long dipole magnet prototypes have been produced and cold-tested at Brookhaven National Laboratory (BNL) and Fermi National Accelerator Laboratory (FNAL) under contract with Superconducting Super Collider Laboratory (SSCL). These magnets are the last phase of a research and development program aimed at demonstrating the feasibility of the 5cm aperture design developed by BNL and FNAL. They are also used as vehicles to transfer technology from the national laboratories to the collider dipole magnet contractors. The BNL magnets, which rely on a horizontally split yoke and the FNAL magnets, which rely on a vertically split yoke, perform according to their somewhat different mechanical design and have equally successful quench performance. Magnets of both designs, however, exhibit a strong sensitivity to the current ramp rate, which appears to be caused by large eddy currents. These is as yet no clear explanation of why the cables used in these magnets show more AC-loss than previous cable. Preliminary investigations reveal possible links to changes in processing of the strand, cable and coil that affect the RRR, ductility, and surface condition of the cable. (author)