Calculation of eddy-currents induced in a compact synchrotron superconducting magnet structure during a current ramp

Under DARPA sponsorship, the compact Superconducting X-ray Light Source (SXLS) is being designed and built by the Brookhaven National Laboratory (BNL). The SXLS machine employs two 180 degrees curved 4-T superconducting dipole magnets. These magnets are required to produce simultaneously a dipole field for bending the beam and finite amounts of higher multipoles which are required for conditioning the beam. In fact, uniformity of the field to less than 1 part in 10000 must be maintained under all operating conditions. When a superconducting magnet is ramped from zero to full field, the changing magnetic field produces eddy currents in the magnet structure which in turn can produce undesirable multipoles. The authors discuss a simple method for estimating these eddy currents and their effect on the field harmonics. They present the analysis basis and its application to the SXLS magnet support structure and to the beam chamber components.<>