  For many next-generation high intensity proton accelerator applications
including the Spallation Neutron Source (SNS), superconducting (SC) RF provides
the technology of choice for the linac. In designing the superconducting
cavity, several features, such as peak fields, inter-cell coupling, mechanical
stiffness, field flatness, external Q, manufacturability, shunt impedance,
higher order mode (HOM), etc., should be considered together. A systematic
approach to determine the optimum cavity shape by exploring the entire
geometric space of the cavity has been found. The most efficient use of RF
energy can be accomplished by adjusting the cell shape. A small region in
parameter space satisfying all reasonable design criteria has been found. With
this design procedure, choosing the optimum shape is simplified. In this paper,
the whole design procedure of this optimisation scheme is explained and applied
to the SNS cavity design.
