A Method to Design Multi-Cell Accelerator Cavities

An efficient method for designing multi-cell accelerator cavities has been developed. It is similar to the approach used by Superfish codes for drift-tube linacs (DTL), where a few single cells at representative beam velocities are tuned in 2D and their geometrical parameters are interpolated to cover the required beam-velocity range. The method is implemented using 3D electromagnetic (EM) modeling with CST MicroWave Studio, which allows its application for various types of resonators, e.g., for H-mode cavities. Interpolating results of 3D EM design of tuned representative single-cell cavities leads to a 3D multi-cell cavity model that can be finalized with just a few small adjustments. As a challenging application example, we design multi-cell resonators of three types - cross-bar (CH) and inter-digital (IH) H-mode, as well as DTL - for accelerating muons in the velocity range of v/c = 0.08-0.3, and compare their performance.