Author: Zhou, D.
Paper Title Page
WEXAT0101 Beam-beam Interaction in SuperKEKB: Simulations and Experimental Results 114
 
  • D. Zhou, Y. Funakoshi, K. Ohmi, Y. Ohnishi
    KEK, Ibaraki, Japan
  • Y. Zhang
    IHEP, Beijing, People’s Republic of China
  
  The beam-beam interaction is one of the most critical factors determining the luminosity performance of SuperKEKB. Simulations and experimental results from SuperKEKB have shown that a complete understanding of the beam-beam effects demands reliable models of 1) the nonlinear beam-beam interaction at the interaction point, 2) the one-turn lattice transfer map with machine imperfections, and 3) other intensity-dependent collective effects. The interplay of these factors makes it difficult to predict the luminosity performance of SuperKEKB via simulations. This paper continues the authors’ previous work* to discuss the beam-beam effects on luminosity in SuperKEKB.
* D. Zhou, Y. Funakoshi, K. Ohmi, Y. Ohnishi, and Y. Zhang, Simulations and Measurements of Luminosity at SuperKEKB, in Proc. IPAC’22, Bangkok, Thailand, Jun. 2022, pp. 2011-2014. 		 
slides icon Slides WEXAT0101 [8.284 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-eeFACT2022-WEXAT0101  
About • Received ※ 26 November 2022 — Revised ※ 06 February 2023 — Accepted ※ 08 February 2023 — Issue date ※ 11 February 2023
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WEXAT0102 Study for -1 Mode Instability in SuperKEKB Low Energy Ring 119
 
  • K. Ohmi, H. Fukuma, T. Ishibashi, S. Terui, M. Tobiyama, D. Zhou
    KEK, Ibaraki, Japan
  
  Emittance increase has been seen in SuperKEKB LER. It is pure single bunch effect: dependent of bunch current but independent of total current. -1 mode signal has been seen in the bunch oscillation recorder at the emittance increase. The emittance increase depends on collimator aperture/impedance and bunch-by-bunch feedback system. We discuss the instability measurement and simulations to explain the phenomenon.  
slides icon Slides WEXAT0102 [2.867 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-eeFACT2022-WEXAT0102  
About • Received ※ 31 October 2022 — Revised ※ 04 February 2023 — Accepted ※ 08 February 2023 — Issue date ※ 15 February 2023
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WEXAT0104
 Beam-beam Simulations including Coupling Impedance  
 
  • Y. Zhang, N. Wang
    IHEP, Beijing, People’s Republic of China
  • M. Migliorati
    Sapienza University of Rome, Rome, Italy
  • K. Ohmi, D. Zhou
    KEK, Ibaraki, Japan
  • M. Zobov
    LNF-INFN, Frascati, Italy
  
  The design performance of future e+e− ring colliders has been pushed to new extreme based on the crab-waist scheme. The new found coherent head-tail instability (X-Z instability) may induce the horizontal beam size blowup and reduce the machine performance. The longitudinal coupling impedance would distort the phase space: lengthen the bunch and bring incoherent synchrotron tune spread. The simulation study has found the clear influence of longitudinal impedance on the X-Z instability in both CEPC and FCCee. With the evolvement of future machine design process, the transverse impedance has also been included. The results show that a vertical beam-beam TMCI-like instability may be induced when the impedance is considered. It is first found in e+e− colliders. Some similar study at SuperKEKB will also be presented. It could be expected or concluded that different effect would couple and determine the final performance together in present and future high performance crab-waist colliders. Separate effect study seems not enough to evaluate and predict the machine performance/stability.  
slides icon Slides WEXAT0104 [3.976 MB]  
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