Experience with Computer Models of Two-Dimensional Magnets

Computer programs have been used extensively in the design studies for a 200-BeV synchrotron. Two magnet codes, SIBYL (originated by Richard S. Christian, then of MURA) and TRIM (originated by Alan M. Winslow of LRL), are currently in use at the Lawrence Radiation Laboratory, Berkeley, for static evaluation of two-dimensional magnets, including finite nonuniform permeability of the iron. In this paper are discussed some of the magnet problems for which the computer codes have been used, and the validity or accuracy of the results. Applications include shaping of the pole for good medium-field profiles and shaping of the pole base to reduce saturation effects. The comparison of calculated and measured fields of the CERN proton synchrotron magnet indicates the attainable quality of computer results. At 14.4 kG, within the limits of the vacuum chamber, the gradient computed by SIBYL was within 1% of the reported gradient.