Electron Cloud Instability Simulation Studies for BEPCⅡ

LIU Yu-Dong; GUO Zhi-Yuan; QIN Qing; WANG Jiu-Qing

Chinese Physics C> 2004, Vol. 28> Issue(11) : 1222-1226

Electron Cloud Instability Simulation Studies for BEPCⅡ

Institute of High Energy Physics,CAS,Beijing 100049,China

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Abstract：
Electron cloud instability (ECI) may take place in a storage ring when the machine is operated with multi-bunch positively charged beam. According to the actual shape of vacuum chamber in BEPCⅡ, a computer simulation program has been developed. With the code, the electron density in the chamber with the different widths of antechamber and the different secondary electron yields, respectively, can be obtained. The possibility to put clearing electrodes in the normal chamber or ante-chamber to reduce the electron density in the central region of the chamber is also investigated. In the simulation, the coherent oscillation of bunches and the formation of electron cloud (EC) are tracked simultaneously. The sideband distribution and growth rate can be obtained through tracking and dealing the bunch oscillation amplitude with FFT. Based on the head-tail model, the single bunch instability induced by EC is also studied. By the simulation, for BEPCⅡ the threshold density for the single bunch instability is estimated to be～10 12 m -3 and the restraining measures that might be adopted in BEPCⅡ can control the EC density under the threshold. According to the simulation results, a relatively big positive chromaticity should be used to suppress the bunch blow up.

References

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. Izawa M et al. Phys. Rev. Lett., 1995, 74, 50442. Fukuma H et al. EPAC2000, 2000, Vienna3. Guo Z Y et al. APAC2004, 2004, Gyeongju4. Ohmi K. Phys. Rev. Lett. 1995, 75: 15265. Furman M A et al. 1997, LBNL-411236. LIU Y D et al. HEP NP, 2004, 28(3): 222(in Chinese)(刘瑜冬等. 高能物理与核物理, 2004, 28(3): 222)7. Bassetti M, Erskine. Report No CERN ISR Th/ 80-06, 19808. Chao A. Physics of Collective Instability in High Energy Accelerators. New York: J. Wiley, 1993

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LIU Yu-Dong, GUO Zhi-Yuan, QIN Qing and WANG Jiu-Qing. Electron Cloud Instability Simulation Studies for BEPCⅡ[J]. Chinese Physics C, 2004, 28(11): 1222-1226.

LIU Yu-Dong, GUO Zhi-Yuan, QIN Qing and WANG Jiu-Qing. Electron Cloud Instability Simulation Studies for BEPCⅡ[J]. Chinese Physics C, 2004, 28(11): 1222-1226. shu

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Received: 2004-04-26
Revised: 1900-01-01

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沈阳化工大学材料科学与工程学院沈阳 110142

Electron Cloud Instability Simulation Studies for BEPCⅡ

Corresponding author: LIU Yu-Dong,

Institute of High Energy Physics,CAS,Beijing 100049,China

Received Date: 2004-04-26
Accepted Date: 1900-01-01
Available Online: 2004-11-05

Abstract: Electron cloud instability (ECI) may take place in a storage ring when the machine is operated with multi-bunch positively charged beam. According to the actual shape of vacuum chamber in BEPCⅡ, a computer simulation program has been developed. With the code, the electron density in the chamber with the different widths of antechamber and the different secondary electron yields, respectively, can be obtained. The possibility to put clearing electrodes in the normal chamber or ante-chamber to reduce the electron density in the central region of the chamber is also investigated. In the simulation, the coherent oscillation of bunches and the formation of electron cloud (EC) are tracked simultaneously. The sideband distribution and growth rate can be obtained through tracking and dealing the bunch oscillation amplitude with FFT. Based on the head-tail model, the single bunch instability induced by EC is also studied. By the simulation, for BEPCⅡ the threshold density for the single bunch instability is estimated to be～10 12 m -3 and the restraining measures that might be adopted in BEPCⅡ can control the EC density under the threshold. According to the simulation results, a relatively big positive chromaticity should be used to suppress the bunch blow up.