| Paper |
Title |
Page |
| TUT1BH2 |
Study of Coherent Head-tail Instablility Due to Beam-beam Interaction in Cirular Colliders Based on Crab Waist Scheme |
61 |
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- K. Ohmi
KEK, Ibaraki, Japan
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FCC-ee is being studied various collision schemes, head-on and large Piwinski angle/ crab waist schemes. We discuss beam-beam limit in the collision schemes using weak-strong and strong-strong models.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT1BH2
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| TUT3AH2 |
Instability Issues in CEPC |
108 |
| |
- N. Wang, W. Chou, J. Gao, D.J. Gong, J. He, Q. Qin, Y.S. Sun, D. Wang, Y. Wang, G. Xu, Y. Zhang, H.J. Zheng
IHEP, Beijing, People's Republic of China
- K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
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The CEPC is a high energy circular electron-positron collider under design. Large bunch population is required to achieve the design luminosity. Instabilities driven by the coupling impedance are possible limitations for reaching high machine performance. An updated impedance model, including the resistive wall and the main vacuum components, has been obtained for the main ring. Based on the impedance model, the collective instability issues of the beam with the partial-double ring design are discussed.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH2
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| TUT3AH5 |
Electron Cloud and Ion Effects and Their Mitigation in FCC-ee |
120 |
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- K. Ohmi, H. Fukuma, M. Tobiyama
KEK, Ibaraki, Japan
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Electron cloud and fast-ion instabilities are serious issues for colliders operated with high current and many bunches. We discuss the instabilities in FCC-ee/hh based on simulations and experiences of KEKB/SuperKEKB.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH5
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| TUT3AH6 |
Electron Cloud at SuperKEKB |
125 |
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- H. Fukuma, K. Ohmi, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan
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Several countermeasures such as ante-chambers, TiN coating, clearing electrodes, grooved structure and so on, have been taken to mitigate the electron cloud effects in the SuperKEKB positron ring. During phase 1 operation of SuperKEKB, which continued from this February to June, the electron cloud effects such as beam size blow-up, non-linear pressure increase, betatron tune shift along a bunch train and transverse coupled bunch instability were observed. Permanent magnets attached at bellows that generate longitudinal magnetic field in vacuum chambers were effective to reduce the electron cloud. This talk will cover following subjects about the electron cloud at SuperKEKB, 1) mitigation methods against the electron cloud, 2) observation of the electron cloud effects in phase 1 operation and 3) plan of further reduction of the electron cloud toward phase 2 operation which will start in the late FY2017.
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| DOI • |
reference for this paper
※ https://doi.org/10.18429/JACoW-eeFACT2016-TUT3AH6
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