Beam instability
Paper Title Page
TUYAA03 Impedances and Collective Effects for JLEIC 90
 
  • R. Li, F. Marhauser, T.J. Michalski
    JLab, Newport News, Virginia, USA
  • K.E. Deitrick
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
JLEIC is the high luminosity and high polarization electron-ion collider (EIC) currently under design at Jefferson Lab. Its luminosity performance relies on the beam stability under high-intensity electron and ion beam operation. The impedance budget analysis and the estimations of beam instabilities are currently underway. In this paper, we present the update status of our back-of-envelope estimations for these collective instabilities, and identify area or parameter regimes where special attentions for instability mitigations are required. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYAA03  
About • paper received ※ 22 October 2018       paper accepted ※ 08 March 2019       issue date ※ 21 April 2019  
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TUYAA04 Study to Mitigate Electron Cloud Effect in SuperKEKB 95
 
  • Y. Suetsugu, H. Fukuma, K. Ohmi, K. Shibata, M. Tobiyama
    KEK, Ibaraki, Japan
  
  During Phase-1 commissioning of the SuperKEKB from February to June 2016, electron cloud effects (ECE) were observed in the positron ring. The electron clouds were considered to exist in the beam pipes in the drift spaces of the ring, where the beam pipes have antechambers and titanium nitride (TiN) coating as countermeasures against ECE. Following this, permanent magnets and solenoids were attached to the beam pipes as additional countermeasures. Consequently, during Phase-2 commissioning from March to July 2018, experiments showed that the threshold beam current for exciting ECE increased by a factor of at least two relative to that during Phase-1 commissioning. While the countermeasures were strengthened, the effectiveness of the antechambers and TiN film coating was re-evaluated. From various simulations and experiments during Phase-2 commissioning, the antechamber was found to be less effective than expected with regard to reducing the number of photoelectrons in the beam channel. The TiN film coating, on the other hand, was considered to have a low secondary electron yield as expected.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYAA04  
About • paper received ※ 27 September 2018       paper accepted ※ 19 February 2019       issue date ※ 21 April 2019  
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TUYBA01 Benchmarking of Simulations of Coherent Beam-beam Instability 103
 
  • K. Ohmi, H. Koiso, Y. Ohnishi
    KEK, Ibaraki, Japan
  • D. El Khechen
    CERN, Geneva, Switzerland
  • K. Hirosawa
    Sokendai, Ibaraki, Japan
  
  Coherent beam-beam nstability in head-tail mode has been predicted in collision with a large crossing angle. The instability is serious for design of future e+e− colliders based on the large crossing angle collision. It is possible to observe the instability in SuperKEKB commissioning. Horizontal beam size blow-up of both beams has been seen depending on the tune operating point. We report the measurement results of the instability in SuperKEKB phaseII commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA01  
About • paper received ※ 25 September 2018       paper accepted ※ 19 February 2019       issue date ※ 21 April 2019  
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