• P. Peiffer, A. Bernhard, F. Burkart, S. Ehlers
  KIT, Karlsruhe
• T. Baumbach, S. Gerstl, A.W. Grau, R. Rossmanith
  Karlsruhe Institute of Technology (KIT), Karlsruhe
• D. Schoerling, D. Wollmann
  CERN, Geneva

The monochromaticity and intensity of synchrotron light emitted by undulators strongly depend on the undulator field quality. For the particular case of superconductive undulators it was shown recently that their field quality can be significantly improved by an array of coupled high temperature superconductor loops attached to the surface of the superconductive undulator. Local field errors induce currents in the coupled closed superconducting loops and, as a result, the hereby generated magnetic field minimizes the field errors. In previous papers the concept was described theoretically and a proof-of-principle experiment was reported. This paper reports results of the first quantitative measurement of the phase error reduction in a 12-period short model undulator equipped with a full-scale induction shimming system.

• P. Peiffer, A. Bernhard, F. Burkart, S. Ehlers, A. Keilmann
  KIT, Karlsruhe
• T. Baumbach, R. Rossmanith
  Karlsruhe Institute of Technology (KIT), Karlsruhe
• D. Schoerling
  CERN, Geneva

In the superconductive undulator SCU14, installed at ANKA, time dependent drifts in the magnetic fields were observed*. Simulations with the software OPERA 3D showed, that the cause of these drifts might be leak and eddy currents in the iron body of the undulator caused by the time-varying currents and fields during current ramps, which slowly decay by ohmic losses. This assumption was crosschecked by measurements at different mockup bodies. This contribution discusses the results of the simulations and measurements and the consequential strategies for avoiding this effect.

* S. Ehlers et. al. "Magnetic field transients in superconductive undulators", in Proceedings of the Particle Accelerator Conference, Vancouver, 2009, to be published.