Computer generated end shims for Recycler Ring magnets

The procedure for automatically producing customized end shims for the Recycler Antiproton Storage Ring gradient magnets is described. Magnets were first measured with a harmonics probe. The observed field defects were then fed into a computer program (initially a spreadsheet) which generated the toolpath code for a numerically controlled milling machine which produced individually customized end shims that eliminated the measured defect. Field defects through decapoles were corrected to an accuracy (limited by the reproducibility of the measurement apparatus) to a few ×10^-5