Optimization of a 118 MHz resonant cavity shape for damping of higher order modes by SiC material

The rf cavity of the storage ring of the Siam Photon Source at National Syn chrotron Research Center (NSRC) in Thailand is modified for the purpose of suppression of higher order modes (HOM) by insertion of SiC material inside the nose cone part. For this purpose, the shape of the nose cone part must be changed. The effect on the modes by the change in shape and the use of SiC is presented and discussed. It is shown that the fields of HOM can be a bsorbed significantly by SiC, which leads to a marked reduction of their Q- values and shunt impedances. This work has been carried out in collaboratio n with the Photon Factory at KEK in Tsukuba, Japan.