• D. Saez de Jauregui, S. Casalbuoni, A.W. Grau, M. Hagelstein, E.M. Mashkina
  FZK, Eggenstein
• R. Cimino, M. Commisso
  INFN/LNF, Frascati (Roma)
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

Recent investigations with the cold bore superconducting undulator installed at ANKA indicate that the main contribution to the beam heat load is caused by electron bombardment. For a quantitative understanding of the problem a cold vacuum chamber for diagnostics has been designed. Among other important parameters (heat load, pressure, etc) this device shall monitor the spectrum of the low energy electrons bombarding the wall. In this contribution we report on the measurements of the spectrum of the low energy electrons bombarding the wall of the cold vacuum chamber in a room temperature region of the ANKA storage ring performed using a in house developed retarding field analyzer (RFA). The calibration of the RFA performed at the national laboratories of Frascati is also described.

• E.M. Mashkina, A.J. Magerl
  University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
• C. Boffo, M. Borlein, W. Walter
  BNG, Würzburg
• S. Casalbuoni, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
  FZK, Karlsruhe
• N. Vassiljev
  University Erlangen-Nuernberg, Institute of Condensed Matter Physics, Erlangen

A new 15 mm period, 1.5 m long planar undulator is being fabricated by Babcock Noell GmbH (BNG) for the ANKA synchrotron light source. In order to qualify the production process and to optimize both the quench protection scheme and the magnetic field correction system, a short prototype has been fabricated. The prototype has been tested in vertical configuration and liquid helium at 4.2K in the CASPER facility at ANKA. The magnetic field has been measured along the beam axis direction by Hall probes with a positioning precision of 3 μm. We report here on the field shimming scheme and the resulting performance of the coils.

• S. Casalbuoni, M. Hagelstein, D. Saez de Jauregui, S. Schleede
  FZK, Eggenstein-Leopoldshafen

Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the prediction obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competitive effects: the photon and electron desorption of the gas contained in the oxide layer of the chamber wall and of the gas cryosorbed, and the cryopumping of the cold surface. We show that photodesorption alone cannot explain the pressure rise observed and that electron multipacting is needed.

• M. Hagelstein, T. Baumbach, S. Casalbuoni, A.W. Grau, B. Kostka, R. Rossmanith, D. Saez de Jauregui
  FZK, Karlsruhe
• A. Bernhard, D. Wollmann
  KIT, Karlsruhe
• J. Chavanne, P. Elleaume
  ESRF, Grenoble
• B. Diviacco
  ELETTRA, Basovizza
• E.M. Mashkina
  University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
• E.J. Wallén
  MAX-lab, Lund

Within the framework of a joint research activity of the European project IA-SFS (RII3-CT2004-506008) four synchrotron facilities have jointly developed diagnostic systems for superconducting undulators. Four work packages have been successfully completed: Design and construction of a test cryostat for field measurements; design and construction of a mock-up coil; field measurement and field error compensation; diagnostics and measurement of the spectrum of low energy electrons responsible for beam heat load in a superconducting undulator. The development advanced the knowledge of magnetic field error compensation considerably and might be of help in understanding the different beam heat load sources. Based on the development a second generation planar superconducting undulator with 15 mm period length for the synchrotron light source ANKA has been specified and procured.

• K.G. Sonnad, I. Birkel, S. Casalbuoni, E. Huttel, D. Saez de Jauregui, N.J. Smale
  FZK, Eggenstein
• F. Caspers
  CERN, Geneva
• A.-S. Müller, K.G. Sonnad
  KIT, Karlsruhe
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

Funding: This work has partly been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.

A superconducting undulator is installed in the ANKA electron storage ring. Electron clouds could potentially contribute to the heat load of this device. A microwave transmission type electron cloud diagnostic has been installed for the undulator section of the ANKA machine. We present the system layout with particular emphasis on the electron machine aspects. Hardware transfer function results and e-cloud data for different machine settings are discussed. Special care has been taken for front end filter design both on the microwave injection and pick-up side.