Higher order modes impedance and damping study for the LHC capture cavity

To investigate the higher order mode (HOM) damping in the LHC 200 MHz capture cavity when using four HOM couplers, simulations have been carried out using both frequency domain and time domain methods. The impedance spectra of the higher order modes in the cavity before and after damping have 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. (5 refs).