Mode analysis of a multilayered dielectric-loaded accelerating structure

In this paper we evaluate a cylindrical metallic waveguide lined with multiple layers of dielectric for use as a slow-wave microwave accelerating structure. A general analysis of this traveling wave, multilayered, dielectric-loaded accelerating structure is presented including field solutions for both the TM (acceleration) modes and HEM (parasitic) modes. Furthermore, we present a recursive design procedure for choosing the layer thicknesses, calculation of the standard accelerator figures of merit such as the quality factor Q and shunt impedance per unit length r, and an easy to implement method for damping the HEM modes. Most importantly, it is shown that this multilayered DLA structure has a dramatically improved attenuation compared to the conventional single-layered dielectric-loaded structure while maintaining comparable shunt impedance. As a numerical example, we compare an 11.424 GHz multilayered structure using 4 layers and an 11.424 GHz conventional single-layered structure.