PBG-slab Embedded Traveling Wave Structure for Planar Beam Accelerator Application

The oversized traveling wave (TE10-mode) channel integrated with the photonic-band-gap (PBG) slab arrays have been investigated for planar beam accelerator application. Simulation analysis showed that the slab arrays allow only the PBG-modes (5 ~ 6 GHz) to propagate with ~ 2 dB of insertion loss, corresponding to ~ 1.14 dB/cm attenuation, which thereby effectively suppresses trapped non-PBG modes down to ~ - 14.3 dB/cm. It will enable monochromatic propagation of fundamental acceleration modes along the heavily overmoded planar waveguide without anomalous excitation of unstable trapped HOMs. The saturated maximum field gradients of the accelerating structure have been analyzed with respect to operational frequency bands corresponding to structural sizes. The field gradient of the guided PBG-mode has been investigated with finiteintegral-method (FIM) simulations at W-band. The quasioptical mode-selective traveling wave structure can efficiently mitigate a beam-breakup problem as lowering the beam-loading with increase of transverse geometrical aspect ratio. This mode-filter could be utilized for HOM dampers in high aspect ratio (HAR) planar beam accelerators. An experimental test is currently under consideration.