Field Correction of an Elliptically Polarized Undulator

The correction of the magnetic field of an elliptically polarized undulator (EPU) decreases the phase errors, the RMS trajectory and multipole magnetic components. The conventional method to correct the field involves tedious work with much trial and error. Based on field-shimming procedures and a field-shimming simulator proposed in National Synchrotron Radiation Research Center, the duration of field correction of EPU46 becomes decreased. The first field integral and the kicker value at each magnet pole determine the amount of adjustment of vertical and horizontal positions of the magnet. The final result of correcting a single pair of a magnet array shows a phase error less than 5 and a variation of the RMS trajectory less than 5 , in both circular and linear polarization modes for single pair of magnet array. Here we describe a standard operating procedure of EPU field correction that is becoming established, which will be beneficial for a future mass-production stage and for training purposes.