Broadband Impedance Calculations and Single Bunch Instabilities Estimations of the HLS-II storage ring

TL;DR

This paper calculates broadband impedances of vacuum chambers in the Hefei Light Source upgrade and analyzes single bunch instabilities, showing the design meets stability thresholds for the target beam current.

Contribution

It provides a comprehensive impedance model for the HLS-II storage ring and evaluates stability thresholds using both analytic and simulation methods.

Findings

Impedance calculations for resistive wall and ceramic chambers

Simulation of wake fields and impedances with CST

Beam stability thresholds exceed current beam requirements

Abstract

The upgrade project of Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber were calculated using the analytic formula, the wake fields and impedances of other designed vacuum chambers have been simulated by the CST code, and then the broadband impedances model was obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities were discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal.