Photonic bandgap structure based accelerating cell

We present detailed calculations of photonic bandgap (PBG) accelerating cavities including estimation of the important effects of an input coupler. The PBG structures consist of a triangular lattice of metal rods containing a single defect on axis. The operating frequency is selected to be 17.1 GHz. The accelerating mode is a quasi-TM₀₁₀ mode localized near the defect. We analyzed the excitation of the cell using a rectangular waveguide with aperture coupling. Both the design of the PBG cell and the design of the input coupling were varied in order to optimize the design. Results are compared with a conventional TM₀₁₀ cavity design. Ohmic loss is found to be comparable for the different cavity designs. The results indicate that the PBG cavity can have the following advantages relative to a conventional cavity: rarified spectrum of modes; oversized dimensions; and simplified input coupling with no frequency shift