Author: Hisamatsu, H.
Paper Title Page
WEYAT0102 Mitigation of Electron Cloud Effect in the SuperKEKB Positron Ring 146
 
  • Y. Suetsugu, H. Fukuma, H. Hisamatsu, H. Ikeda, T. Ishibashi, K. Kanazawa, K. Ohmi, K. Shibata, M. Shirai, S. Terui, M. Tobiyama
    KEK, Ibaraki, Japan
  • Y.M. Lee
    Sokendai, Ibaraki, Japan
 
  One critical issue for the SuperKEKB is the electron cloud effect (ECE) in the positron ring, and various countermeasures had been prepared before starting the commissioning. The ECE, however, was observed during phase-1 commissioning (2016) caused by the electron cloud in the beam pipes at drift spaces of the ring, which had antechambers and a TiN-film coating. Permanent magnets and solenoids to generate magnetic fields in the beam direction were attached to the beam pipes as additional countermeasures before the next phase-2 commissioning (2018). Consequently, the threshold of the current linear density for exciting the ECE increased by a factor of at least 2. During Phase-3 commissioning (2019), it was confirmed that the threshold was over 0.53 mA/bunch/RF bucket, and we have observed no clear evidence of ECE in the usual operation up to now. The effectiveness of the ante-chambers and TiN film coating of the real beam pipe was reevaluated. The present ante-chambers were found to be less effective than expected with regard to reducing the number of photoelectrons in the beam channel. Here we will summarize the mitigation techniques used in the SuperKEKB and the results so far.  
slides icon Slides WEYAT0102 [7.521 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-eeFACT2022-WEYAT0102  
About • Received ※ 22 September 2022 — Revised ※ 04 February 2023 — Accepted ※ 08 February 2023 — Issue date ※ 11 February 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THXAS0102 Status and Experiences of Vacuum System in the SuperKEKB Main Ring 236
 
  • T. Ishibashi, H. Hisamatsu, K. Kanazawa, K. Shibata, M. Shirai, Y. Suetsugu, S. Terui
    KEK, Ibaraki, Japan
  • Y.M. Lee
    Sokendai, Ibaraki, Japan
 
  Since the start of SuperKEKB operation in 2016, the stored beam currents have gradually increased in the main ring. In the commissioning of 2022 spring, the maximum beam currents were ~1460 mA in the low energy ring for positron (LER) and ~1145 mA in the high energy ring for electron (HER). The beam doses up to now have been ~ 7312 Ah in LER and ~6199 Ah in HER, and the vacuum scrubbing of the beam pipes is proceeding well. On the other hand, during these operations, problems such as abnormal pressure rises, vacuum leaks, collimator damages and so on have occurred. Here, we mainly report on the experiences and status in the vacuum system after the commissioning in the spring of 2019 named Phase-3, especially.  
slides icon Slides THXAS0102 [16.386 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-eeFACT2022-THXAS0102  
About • Received ※ 28 October 2022 — Revised ※ 04 February 2023 — Accepted ※ 07 February 2023 — Issue date ※ 19 February 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)