Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
To investigate the higher order mode (HOM) damping in the LHC 200MHz capture cavity when using four HOM couplers, simulations have been done by both frequency domain and time domain methods. Using these methods the impedance spectra of the higher order modes in the cavity before and after damping has been obtained. From this, detailed information about the HOM coupler's contribution to HOM.damping can be obtained. The distribution and magnitude of some potentially dangerous higher order modes in the LHC capture cavity have been found.