Investigation of Geometric Variations for Multicell Cavities Using Perturbative Methods

The design of multicell accelerator cavities is a challenging task, since it implies the manipulation of various shape parameters regarding different (partially contradicting) optimization goals. Simulating the electromagnetic characteristics of the full structure depending on various geometric parameters typically involves an enormous computational effort. In most cases, this limits the observed frequency range and the number of optimization passes. For the same reason, the effects of unintended shape deviations are usually excluded from the optimization processes, even though they may be of particular importance for the final design. Perturbative methods offer an efficient approach to tackle this issue. They allow the computation of the eigenmodes and the derived cavity performance parameters for a vast number of cavity designs based on one initial design. In this paper, we investigate the applicability of perturbative methods for performance optimization and simultaneous consideration of the shape variations of a multicell structure.