Impedance budget and instability estimation of the HLS-II storage ring

TL;DR

This paper models the broadband impedance of the HLS-II storage ring using simulations and theoretical analysis to estimate beam stability and inform vacuum chamber design improvements.

Contribution

It introduces a comprehensive impedance model combining simulations and theory to evaluate beam stability in the HLS-II storage ring.

Findings

Broadband impedance was successfully modeled using CST simulations and FFT.

The designed vacuum chambers increased the instability threshold beyond the beam current goal.

Theoretical analysis confirmed the stability of the upgraded storage ring.

Abstract

The upgrade project of Hefei Light Source storage ring is under way. In this paper, the wake fields of new designed vacuum chambers have been simulated by CST code, and then broadband impedances were obtained by FFT. Together with resistive wall wake fields, broadband impedance model for storage ring was established. Using theoretical formula, longitudinal and transverse single bunch instabilities were discussed. With carefully-designed vacuum chamber, the threshold of beam instabilities was higher than beam current goal.