Abstract
An electron cloud induces a wake force on a charged particle beam which creates correlations between bunches---i.e., a small displacement of a bunch creates a perturbation of the electron cloud, which affects the motions of the following bunches, with the result that a coupled-bunch instability is caused. The coupling mode of the instability is determined by the motion of the electrons in the cloud---that is, it depends on which electrons, moving in a drift space, a weak solenoid field or a strong bending field, are dominant for the instability. We discuss the coupled-bunch instability focusing on the relation between the mode spectrum and the electron motion.
Highlights
A positron or proton beam creates electrons due to synchrotron radiation, beam particle loss, and secondary emission due to the absorption of primary electrons at the vacuum chamber surface
We discuss the coupled-bunch instability caused by electron clouds in drift spaces, weak solenoids and strong bending magnets using aanalytic method based on the wake force and particle tracking simulation in this paper
We have studied the coupled-bunch instability caused by electron clouds
Summary
A positron or proton beam creates electrons due to synchrotron radiation, beam particle loss, and secondary emission due to the absorption of primary electrons at the vacuum chamber surface. An experiment performed at the KEKB LER showed that the solenoid magnets strongly affected the coupled-bunch instability, and a simulation followed the experimental results [5]. We discuss the coupled-bunch instability caused by electron clouds in drift spaces, weak solenoids and strong bending magnets using a (semi)analytic method based on the wake force and particle tracking simulation in this paper. The results tell us that the mode spectrum of the coupled-bunch instability indicates which electrons, in drift spaces, solenoid magnets, bending magnets or other magnets, are dominant in the actual ring. The growth rate of each coupled-bunch mode is evaluated from the wake force in.
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