Shaping of pole ends to minimize field errors in quadrupole magnets

Starting from the Laplace equation for the scalar potential, a procedure was developed which allows computation of multipole-free magnetic-pole profiles. Fields of the magnet energizing coils were not taken into account. Three alternative processes to manufacture these poles using NC milling and laser cutting machines were outlined. The results of field mapping and multipole analysis of quadrupole magnets with such poles showed a reduction of the dodeca- and icosapole components by a factor of 5 to 6. Deviations of the measured gradient curve from the computed one are observed in the low-field region outside the magnets.