Field integral shimming of elliptically polarized undulator at Shanghai synchrotron radiation facility

This paper discusses the shimming and the optimization algorithm of the integrated multipoles and the first and second field integrals of the EPU100 at Shanghai synchrotron radiation facility. To shim the integrated multipoles, the “Magic Fingers” technique is used, which is a proper arrangement of small magnet cylinders to reduce variation of the field integral errors; and the 8 trimming coils installed at the two ends of the undulator are used to shim the first and second field integrals. After shimming all the operating gaps or polarized modes of the EPU100, the quadrupole component is less than 9×10-3 T, the sextupole component is less than 1.6 T/m, and the octupole component is less than 30 T/m2, the multipole components are all well within the specifications.