Measures to mitigate the coherent beam-beam instability at CEPC

TL;DR

This paper investigates methods to mitigate coherent beam-beam instabilities at CEPC, analyzing chromaticity, resistive feedback, and hourglass effects through simulations to enhance collider stability.

Contribution

It provides a comprehensive analysis of instability mitigation strategies including chromaticity adjustments and feedback systems for CEPC.

Findings

Chromaticity and asymmetrical tunes can suppress vertical instability.

Resistive feedback effectively mitigates beam-beam instabilities.

Hourglass effect influences the effectiveness of mitigation measures.

Abstract

Both horizontal and vertical coherent beam-beam instability are important issues at CEPC. The horizontal instability (X-Z instability) could be induced by beam-beam itself. In this paper we try to study the effect of chromaticity and resistive feedback by analysis and simulation. The vertical instability may be induced due to the combined effect of beam-beam interaction and vacuum impedance. Finite chromaticity and asymmetrical tunes have been proposed to suppress the vertical instability. Due to the further increase of impedance budget, we need to find more measures to mitigate the instability. The effect of resistive feedback and hourglass effect are evaluated by simulation.