Beam instability due to higher-order modes of APS cavities in the Tristan accumulation ring

Abstract

Shifts of resonant frequencies of the APS cavity were measured as a function of the tuner position and cavity temperature. From this measurement we found that cavity temperature warm-up plays an important part concerning coherent instability. There was evidence that the accumulation current was limited by resonance with higher-order modes. We could identify which cavity mode was responsible for the transverse coherent instability.