A FOUR-CELL PERIODICALLY HOM-DAMPED RF CAVITY FOR HIGH CURRENT ACCELERATORS *

A periodically Higher Order Mode (HOM) damped RF cavity is a weakly coupled multi-cell RF cavity with HOM couplers periodically mounted between the cells. It was studied as an alternative RF structure between single-cell and superstructure cavities in high current application requiring strong damping of HOMs. The acceleration mode in this design is the lowest frequency mode (zero mode) in the pass band, in contrast to the traditional “π” acceleration mode in multicell superconducting cavities. The acceleration mode of the four-cell cavity has been studied, along with the monopole and dipole HOMs. The frequency response through HOM ports has been simulated in HFSS ™ with waveguide couplers, which shows almost constant Qext for several important HOMs, even with different number of cells. A 4x1 zero-mode cavity was studied with MAFIA time domain analysis. To understand the tuning challenge for this weakly-coupled cavity, ANSYS ® and SUPERFISH codes were used to simulate the cavity frequency sensitivity and field flatness change, which will influence the design of the tuner structure. This paper presents the computer simulation of this novel accelerating structure that may be used for variety of accelerator applications