Tunable wakefield dielectric-filled accelerating structure

The feasibility of the frequency spectrum of Vavilov-Cherenkov radiation being controlled in a wakefield dielectric-filled accelerating structure via an outer ferroelectric layer is studied. The spectrum and amplitude of the field excited in the structure versus the permittivity of the ferroelectric are found. Dielectric losses in the ferroelectric are estimated. It is shown that these losses impose limitations on the ferroelectric layer thickness and the range within which the frequency spectrum of the waveguide can be controlled. The structure under consideration is optimized for the AWA wakefield accelerator. The multilayer construction of the waveguide, in combination with specially shaped ferroelectric-permittivity-controlling electrodes, allows designers to tune the spectrum of the waveguide and suppress electron-bunch-deflecting waveguide modes. Thereby, there appears the possibility of controlling the transverse stability of the beam.