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Title Impedance Considerations for the Design of the Vacuum System of the CERN PS2 Proton Synchrotron Submitted 08-DEC-09 20:13 (UTC)
Classification 04 Hadron Accelerators Modified 08-DEC-09 22:13 (UTC)
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Presenter Karl Leopold Freitag Bane Paper ID MOPD017
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Author(s) Karl Leopold Freitag Bane, Gennady Stupakov, Ulrich Wienands (SLAC, Menlo Park, California), Michael Benedikt, Alexej Grudiev, Edgar Mahner (CERN, Geneva)
Abstract In order for the LHC to reach an ultimate luminosity goal of 10^35, CERN is considering upgrade options for the LHC injector chain, including a new 50 GeV synchrotron of about 1.3 km length for protons and heavy ions, to be called the PS2. In this ring the proton energy is ramped from 4 GeV in 1.2 s, and the design (proton) current is 2.7 A. The present baseline of the vacuum system considers elliptical stainless steel chambers bakeable up to 300°C, various coatings to mitigate electron cloud are under study. For a bare stainless steel or Inconel chamber, the resistive wall wake alone will lead to multi-bunch instability, whereas for transverse mode coupling (TMCI), the threshold is above the design beam current, though this instability may become an issue once other impedance contributions are taken into account. A copper layer of varying thickness is shown to raise the TMCI threshold but to have relatively little effect on the multi-bunch resistive-wall growth rate unless the coating is very thick. We are also studying the effect of the copper coating on the penetration of the guide field during the energy ramp, which sets an upper limit on the allowable thickness.
Word Count: 199  Character Count: 1166
Funding Agency This work supported in part by the US DOE through the US LHC Accelerator Research Program (LARP).

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