A review of magnetic field measurements of full scale conduction cooled superconducting undulator coils

Synchrotron light sources employ undulators to produce brilliant photon beams. Most synchrotrons and all free electron lasers use undulators made by permanent magnets. Superconducting undulators can produce, for the same geometry, a higher peak magnetic field on axis with respect to permanent magnet ones, and have the additional advantage of being radiation hard. Recently superconducting undulators have been successfully applied in the Karlsruhe Institute of Technology synchrotron and in the Advanced Photon Source at the Argonne National Laboratory. While precise measurement techniques to characterize the magnetic field for permanent magnet undulators are well established, new developments have been necessary in the past few years to magnetically characterize superconducting undulators. After an introduction on undulators and the measurements needed to be performed before operating such devices with electron beams, this paper reviews magnetic field measurements of full scale conduction cooled superconducting undulator coils. Current and future methods used for the characterization of the magnetic field, after installation of such coils in the final cryostat, are also discussed.