CAS, Inst High Energy Phys, Beijing 100039, Peoples R China
; High Energy Accelerator Res Org KEK, Tsukuba, Ibaraki 3050801, Japan
To investigate the higher order mode (HOM) damping in the BEPC II superconducting cavity (SC) when using HOM absorbers, simulations have been done for changing the position and the length as well as the thickness of ferrite of HOM damper, and for different positions and angles of taper. The optimized values under which the HOM impedance of the BEPC II SC cavity will be trapped in the impedance threshold of the BEPC II collider have been found. For verifying the simulation result mentioned above, HOM measurements on the BEPC II model cavity have been made, and the satisfied results for HOM damping are obtained. The distribution, and magnitude of some potentially dangerous higher order modes have been found, which are basically consistent with the simulations.