Tuning of X-band traveling-wave accelerating structures

This paper derives and explains the full procedure used to tune an X-band traveling-wave accelerating structure from the “bead-pull” measurement data. The local reflection of each cell caused by frequency detuning is calculated from the measured field profile deduced from the reflection from a dielectric perturbation (so-called “bead”) and is corrected by monitoring the input reflection coefficient. The structure output matching is made by tuning the last two cells to cancel the reflected wave. This method also gives the relationship of the reflection and frequency detuning, making it possible to evaluate the dimensional tolerances achieved in manufacture.