Influence of vacuum chamber port terminations on beam coupling impedances

Vacuum chambers of particle accelerators are typically equipped with radio-frequency couplers. The couplers employed to excite modes for acceleration, extract the energy higher-order modes, or diagnostic purposes. From a network theory perspective, these represent terminal ports by which means structure can exchange its exterior. Usually, terminated fixed impedances corresponding characteristic coaxial lines attached them. In this paper, we investigate influence termination conditions vacuum on beam coupling impedances. For purpose, introduce novel approach that allows us determine arbitrary port terminations. A full-wave Maxwell solver is generalized scattering matrix chamber and prespecified reference Often, chosen be line waveguides so coupler free reflection. Using matrix, readily determined computationally inexpensive postprocessing step takes into account impedance loads at ports. Thus, various terminations conveniently examined. This relevant improve older structures were designed when no sophisticated design tools available operation existing purpose they initially not for. proposed approach, 33-cell 200 MHz traveling-wave accelerating SPS CERN. It shown do have an important and, therefore, must taken in stability considerations.