Bahrdt, J.; Fentrup, W.; Gaupp, A.; Scheer, M.; Balewski, K.; Keil, J.; Schoeps, A.; Tischer, M.: Performance of the PETRA III APPLE II Undulator. In: Proceedings of IPAC2011, 4 - 9 September 2011, San Sebastián, Spain.. , 2011, p. 3254-3256

Abstract:
A 5m-long APPLE II undulator has been built in collaboration between Helmholtz-Zentrum Berlin and DESY Hamburg. Magnetic field measurements after the final shimming in the laboratory are presented. The device has been installed in the storage ring and machine studies have been performed. The tune shifts in the elliptical and the inclined mode are in agreement with predictions from theory. The dynamic field integrals have successfully been minimized in the storage ring with so-called L-shims (rectangular iron sheets) which are placed at the undulator center at the magnet edges