Magnetic Field Measurements of Full-Scale Conduction-Cooled Superconducting-Undulator-Coils

The Institute for Beam Physics and Technology (IBPT) of the Karlsruhe Institute of Technology (KIT), and the Babcock Noell GmbH are collaborating to develop superconducting undulators for ANKA and low-emittance light sources. The collaboration is now focusing on a superconducting undulator with a period length of 20 mm (SCU20) planned to be the source of the NANO beamline at ANKA. The local magnetic field and the field integrals of the SCU20 1.5-m-long-coils have been characterized in a conduction-cooled horizontal test facility developed at KIT IBPT. Here we complement the main results reported in a previous work with a more detailed analysis, including the measurements of the geometrical deviations from the ideal case of the undulator coils at room temperature used to simulate the magnetic field profile with the program Radia and a quantitative explanation of the magnetic field measurements in cold conditions. A comparison of the photon spectrum calculated from the measured field with the one from the field simulated with Radia considering the geometry measured at room temperature is also presented.