Effect of HOM Couplers on the Accelerating Mode in the Damped Cavity at the Photon Factory Storage Ring

Effect of a rod type HOM coupler on the accelerating mode in a normal conducting single cell cavity was studied by using MAFIA. Usually, this type of coupler is used to reduce Q-values of some HOMs such as TM011, TM111, TE111, TM021-like modes which have strong E-field in the middle of cylindrical wall of the cavity. We are trying to use this rod type HOM coupler in the off-centred position on the cylindrical wall in order to make it effective for other HOMs such as TM012, TM022-like modes. When it is attached to the position apart from the middle of the cylindrical wall, the coupling with the fundamental mode should be taken into account. Therefore we studied the effect of the rod type HOM coupler on the fundamental mode by the use of MAFIA. The results are presented.