References on  incoherent Electron Cloud effects,

the electron pinch, and the effect of synchrotron motion

compiled in chronologic order by F. Zimmermann

R&D and LHC Collective Effects

A team of the CERN AB-ABP Group

• M.A. Furman and A.A. Zholents, Incoherent Effects driven by the Electron Cloud, presented at PAC 99, New York City. The two authors study the tune shift and synchro-betatron resonances driven by the electron-cloud pinch - which is similar to the resonance trapping, and appears just to be a different way to look at the same problem. They conclude that this is not a strong effect for the PEP-II B factory.
• In the fall of 1999 Katsunobu Oide hypothesized an incoherent effect as explanation of the KEKB blow up. The KEKB case was however soon shown to be dominated by the fast blow up due to the TMC-like instability, an explanation which Kazuhito Ohmi and Frank Zimmermann proposed at Christmas 1999, and which was afterwards proven experimentally. Nevertheless it now looks as if there is a small incoherent effect below the fast-instability threshold. Katsunobu's proposal might be found in one of the KEKB MACs. Certainly he discussed it with Frank Zimmermann at the end of 1999. He suspected that a spurious dispersion was generated by the cloud, but he was also worried about the "pinch".
• F. Zimmermann, Electron Cloud Simulations: An Update, Chamonix 2001. Included in this paper was an estimate of the incoherent tune shift due to electron cloud at the end of a bunch passage.
• G. Rumolo, F. Zimmermann, "Electron-Cloud Instability with Space Charge or Beam Beam", 3rd paper in Contributions of the SL-AP Group to the Two-Stream Instabilities Workshop. CERN-SL-2001-067, or see the TWO-STREAM 2001 workshop proceedings. Here a few-particle model is developed which includes the tune shift from space charge, from electron-cloud, plus the synchrotron motion.
• K.V. Lotov, G.V. Stupakov, Single-Bunch Instability of Positron Beams in Electron Cloud , EPAC 2002, Paris. The two authors find a strong incoherent effect, but their simulation later turned out to be mistaken (private communication by Gennady Stupakov in 2004).
• K. Ohmi, Single Bunch Electron Cloud Instability for a Round Beam, Memorandum, November 2002. In this memo, Kazuhito Ohmi discusses the incoherent effect, and he says 'it may be like space-charge effect'.
• K. Ohmi, Single Bunch Electron Cloud Instability for a Round Beam II, Memorandum, December 2002,

  Kazuhito here continues the analogy with space charge and interestingly enough he considers the effect of a linear stopband resonance due to a quadrupole error.
• E. Benedetto, et al. Transverse 'Monopole' Instability driven by Electron Cloud?, PAC 2003, CERN-AB-2003-036-ABP (2003).  In this paper, the Lotov-Stupakov result cannot be reproduced, but the large tune footprint created by the pinched electron cloud is calculated, by frequency maps, which reveals several resonances potentially contributing to the incoherent emittance growth. Also simulations with different synchrotron tunes are compared.
• E. Benedetto and F. Zimmermann, Analysis of the Electron Pinch during a Bunch Passage, Proceedings ECLOUD'04 April 2004. Here we compute analytically the incoherent tune shift as a function of longitudinal and transverse position along the bunch, assuming that this could be responsible for incoherent emittance growth.
• Analogies between resonance-trapping phenomena which may explain beam losses observed at the CERN PS (due to space charge) and at the SPS (due to electron cloud) were hinted at in September 2004 during discussions at CERN in connection with the ICFA-HB2004 workshop and later brought forward at the CARE HHH-2004 workshop by Giuliano Franchetti, Elias Métral, and Frank Zimmermann. At the HHH-2004 workshop also the strong dependence of the simulated emittance growth on the localization of e-cloud kicks along the ring was explained by Elena Benedetto and Giuliano Franchetti.
• K. Ohmi, Incoherent Beam Size Blow Up ..., Chaos and Emittance Growth, KEK Acc-Physics Seminar 25 March 2005. This is interesting and almost agrees with the trapping model of Giuliano Franchetti et al. Kazuhito here explains the emittance growth in terms of 6D Arnold diffusion.
• E. Benedetto,  G. Franchetti, K. Ohmi,  D. Schulte,  F. Zimmermann, Emittance growth caused by electron cloud below the "fast TMCI" threshold: numerical noise or true physics?, PAC2005 Knoxville, LHC Project Report 826. This paper describes the application of Giuliano Franchetti's resonance-trapping model to the electron-cloud problem.

Last modified on 04/06/2006 11:46  by or