Impedance estimation and instability analysis for Korea-4GSR storage ring

Korea-4GSR is a future light source in Korea with a circumference of 800 m, an energy of 4 GeV, and a maximum current of 400 mA. Due to the small aperture of the vacuum chamber (12H x 9V octagonal) and the large number of normal-conducting cavities and beam position monitors (BPMs), impedance-induced instabilities are expected to pose challenges at 400 mA operation. In this study, we estimated the storage ring impedance of Korea-4GSR and investigated both single-bunch and multi-bunch instabilities to determine optimal operational conditions, including the analysis of fill patterns