Numerical studies on tuning of a traveling wave bunching-cum-accelerating structure in simulation environment

Abstract

We have explored the 3D electromagnetic code CST-MWS to comprehend the tuning of a Traveling Wave (TW) bunching-cum-accelerating structure. End-to-end electromagnetic (EM) simulations of an ideal structure have been performed to study its RF characteristics, including the complete profile of on-axis electric field magnitude and phase. Errors are then deliberately introduced in the cell geometry of TW linac, and its effect on the magnitude and phase of electric field along the linac has been investigated in a simulation environment. Taking the electric field data from the EM simulation of the structure, the required correction in each cell has been calculated using a tuning program, in order to nullify the effect of the introduced geometric error. It is shown that after application of these corrections, the correct profile of electric field magnitude and phase along the linac is restored, thereby validating the tuning methodology in the simulation environment. Such studies are useful for validating the tuning algorithm before adopting it in laboratory, and also for predicting the phase errors for any given combination of geometrical errors introduced due to machining, brazing or thermal distortion; thereby setting the tolerances on geometrical errors, while designing a structure.