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Hagelstein, M.

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OPR03 Can Electron Multipacting Explain the Pressure Rise in the Cold Bore ANKA Superconducting Undulator? 12
 
  • S. Casalbuoni, S. Schleede, M. Hagelstein, D. Saez de Jauregui, P. Tavares
    Karlsruhe Institute of Technology
 
  Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA (Angstrom source Karlsruhe) 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 predictions 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 competing effects: the photon and electron stimulated desorption of the gas contained in the surface layer of the chamber wall and of the gas cryosorbed, and the cryopumping by the cold surface. We show that photodesorption alone cannot explain the experimental results and that electron multipacting is needed to reproduce the observed pressure rise. Electron bombardment can at the same time explain the observed beam heat load.  
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DIA04 Status of COLDDIAG: a Cold Vacuum Chamber for Diagnostics 190
 
  • S. Gerstl, T. Baumbach, S. Casalbuoni, A. Grau, M. Hagelstein, D. Saez de Jauregui
    Karlsruhe Institute of Technology
  • R. Cimino, M. Commisso, B. Spataro, A. Mostacci
    INFN/LNF
  • J. Clarke, D. Scott
    Science and Technology Facilities Council (STFC/DL/ASTeC) Daresbury Laboratory Accelerator Science and Technology Centre
  • M. Cox, J. Schouten
    Diamond Light Source Ltd (Diamond)
  • R. Jones, I. Shinton
    Cockcroft Institute
  • E. Wallen
    Lund University - MAX-Lab
  • R. Weigel
    Max-Planck Institute for Metal Research, Stuttgart
  • V. Baglin
    CERN
  • C. Boffo, G. Sikler
    Babcock Noell GmbH (BNG)
  • T. Bradshaw
    Science and Technology Facilities Council (STFC/RAL) Rutherford Appleton Laboratory
 
  One of the still open issues for the development of superconducting insertion devices is the understanding of the heat load induced by the beam passage. With the aim of measuring the beam heat load to a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. We plan to have access with the same set-up to a number of different diagnostics, so we are implementing: i) retarding field analyzers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics. A first installation in DIAMOND is planned in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.  
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