Simulations on the Fast-beam Ion Instability at the PLS

Abstract

The fast-beam ion instability is a. significant issue in an electron storage ring. In this paper, a weak-strong simulation code is used to simulate the fast-beam ion instability at the in-vacuum undulators of the Pohang Light Source (PLS) and the PLS-II. The growth time of the vertical oscillation amplitude is calculated for various vacuum pressures. Above the threshold vacuum pressure, the vertical oscillation amplitude exceeds the vertical beam size. The effect of a feedback system is investigated and shows that bunch-by-bunch feedback of 50 turns is effective in suppressing the growth of the vertical oscillation amplitude.