CAS, Inst High Energy Phys, Beijing 100049, Peoples R China
Superconducting (SC) RF technology is an excellent choice for International Linear Collider (ILC), and the whole cost of ILC is closely related to the gradient of SC cavity. However, the gradient of Nb SC cavity is limited by SRF critical magnetic field at present. So it is very necessary to optimize the cavity shape to decrease the ratio of surface peak magnetic field and accelerating gradient (H-p/E-acc). A serial of new cavity shapes have been proposed including Low Loss shape and Re-Entrant shape etc. Low Loss shape has lower HIE,,, than Re-Entrant shape, so theoretically Low Loss shape can reach higher gradient. In this paper, an optimal design is illustrated. Then a Low Loss SC Cavity shape and its calculation results are presented, and finally these results are compared with TESLA 800 cavity and Re-Entrant Cavity.