Stretched wire measurement of multipole accelerator magnets

Theoretical aspects of stretched wire field integral measurements are investigated. A least square approach is used for the processing of the measured signal; it can be applied to any wire trajectory and it allows numerical correction of the wire position errors. Moreover, the signal from some multipoles can be compensated for in a way comparable to the “bucked” rotating coil method. This can be used for accurate measurements of field multipole errors. A stretched wire bench has been built at the European Synchrotron Radiation Facility. This bench has been used for measuring dipole, quadrupole, and sextupole magnets. The results obtained with various wire trajectories are compared. It is demonstrated that an accuracy of a few 10^-4 of the main multipole can be obtained.