Corrector-based magnet alignment procedure

A method of realigning the quadrupole magnets in storage rings to achieve minimum dipole corrector strengths is described. The corrector strengths after realignment are mainly determined by Beam Position Monitor offsets relative to the quadrupole magnets they have been calibrated against and the extent to which magnet dipole errors stay constant during the realignment. The accuracy to which quadrupole misalignments can be determined is mainly limited by dipole errors not originating from quadrupole displacements and the accuracy to which BPM offsets can be determined. After realigning a ring by the described method, any subsequent realignment with the aim to compensate for long-term magnet movements can be performed with greater accuracy. The method was applied at the MAX III storage ring and the magnet positions were then measured in the conventional way with a laser tracker. The difference between the two methods is discussed. Finally, the realignment result was compared with simulated results for two different MAX III test cases.