Higher-order modes in periodic accelerating structures analyzed using the cavity mode method

The cavity mode method is a new method for computing the dispersion curves and fields of accelerating structures. The method assumes that the field of interest is expanded with open and short modes. These modes are constructed on the basis of the resonant fields in a unit cell. With the wave equation and the Floquet boundary conditions, the method is mathematically simplified into a general eigenvalue problem to calculate the dispersion curve and fields for any phase shift in the structures. This method has been used in analyzing the higher-order modes in the periodic structures. In further study, it is also expected to be useful for analyzing non-periodic structures in the next generation linear collider.