CAJ | 학술논문

正电子储存环在多束团运行时有可能发生电子云不稳定性(ECI).本文针对北京正负电子对撞机二期工程(BEPCⅡ)的具体条件,编写发展了模拟计算程序,以不同电子云密度抑制措施下的计算结果为基础,研究了耦合束团不稳定性和单束团不稳定性,给出了电子云不稳定性增长率和阈值密度以及色品对束团尺寸增长的抑制作用,为储存环中电子云不稳定性的前沿科学研究和BEPCⅡ工程设计提供了有意义的结果.
정전자저존배재다속단운행시유가능발생전자운불은정성(ECI).본문침대북경정부전자대당궤이기공정(BEPCⅡ)적구체조건,편사발전료모의계산정서,이불동전자운밀도억제조시하적계산결과위기출,연구료우합속단불은정성화단속단불은정성,급출료전자운불은정성증장솔화역치밀도이급색품대속단척촌증장적억제작용,위저존배중전자운불은정성적전연과학연구화BEPCⅡ공정설계제공료유의의적결과.
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 BEPC Ⅱ , 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 BEPC Ⅱ the threshold density for the single bunch instability is estimated to be ～ 1012m - 3and the restraining measures that might be adopted in BEPC Ⅱ 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.