Preliminary results of the Scrubbing Run 2004

by G. Arduini and J. Jimenez

Thursday 22 Jul 2004, 11:00 → 12:00 Europe/Zurich

SL Auditorium (CERN)

Because of the tight bunch spacing, the LHC beam induces multipacting in the SPS vacuum chamber and an electron cloud builds up along the LHC bunch train. The resulting electron bombardment at the vacuum chamber surface is responsible for dynamic pressure rises and fast transverse instabilities. The critical parameter for the onset of the beam-induced multipacting is the Secondary Electron Yield (SEY) of the vacuum chamber surface. A sizeable reduction of the SEY can be obtained by beam induced electron bombardment ('scrubbing'). Dedicated scrubbing runs (~10 days in the early part of the run) have become part of the SPS accelerator programme since 2002. These machine runs have been used to increase the threshold bunch population for the onset of electron multipacting in the SPS but in particular they have provided significant input to understand the electron cloud build-up and to bench-mark simulations to increase the reliability of the extrapolations to the LHC. This has been possible thanks to the conception and installation of dedicated electron cloud monitors in the SPS as a result of the collaboration between the AB and AT departments and thanks to the advances in the understanding of the LHC beam behaviour in the presence of electron cloud. An overview of the tools developped so far and of the results obtained, in particular during the last scrubbing run, will be presented.


Organiser(s): Werner Herr (AB/ABP)
More information: http://cern.ch/AB-seminar/

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