Paper |
Title |
Page |
WEPIK075 |
Electron Cloud Instability in SuperKEKB Phase I Commissioning |
3104 |
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- K. Ohmi, J.W. Flanagan, H. Fukuma, H. Ikeda, E. Mulyani, K. Shibata, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan
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Beam size blow-up due to electron cloud has been observed in Phase I commissioning of SuperKEKB. Vacuum chambers in LER (low energy positron ring) were cured by antechamber and TiN coating for electron cloud. Some parts, bellows, were not cured by the coating. In the early stage of Phase I commissioning, beam size blow up has been observed above a threshold current. The blow up was suppressed by weak permanent magnets generating longitudinal field, which cover the bellows. Electron cloud current have been monitored during the commissioning. The thresholds for the electron cloud induced fast head-tail instability have been simulated in the operating beam conditions. Coupled bunch instability caused by electron cloud has been measured in the operating beam conditions and installation of the permanent magnets. The measurement and simulation results are presented.
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DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK075
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THPAB022 |
Ion Instability in SuperKEKB Phase I Commissioning |
3741 |
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- K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan
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Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.
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DOI • |
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※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022
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THPVA012 |
Transverse Impedance Measurement in SuperKEKB |
4442 |
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- N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
- T. Ishibashi, T. Mimashi, K. Ohmi, Y. Ohnishi, K. Shibata, Y. Suetsugu, S. Terui, M. Tobiyama, D. Zhou
KEK, Ibaraki, Japan
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In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×1035 cm-2s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.
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DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA012
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