Photonic band gap structures for accelerator applications

We report the results of our theoretical investigation and cold test of a two-dimensional (2D) metal photonic band gap (PBG) accelerator cell and propose to construct a 2pi/3 linear accelerator structure with reduced wakefields as a stack of PBG cells set between disks with irises. We developed a computer code, called Photonic Band Gap Structure Simulator (PBGSS), to calculate the complete dispersion curves for square and triangular arrays of metal rods [1]. Using the PBGSS code, the global photonic band gaps of the arrays were determined and employed to design the PBG cavities. The modes of the 2D PBG cavity formed by a defect, (missing rod) in the triangular array of metal rods were studied numerically using the HFSS [2] code. The cavity was designed with only the fiandamental TM01 mode confined and higher order modes suppressed. The cold test was performed and the results proved the suppression of the wakefields. Dielectric PBG structures were also studied as applied to microwave devices. A dielectric PBG resonator with the TM02 mode confined and TM01 and TM11 modes absent was designed. The construction of such a resonator overcomes the problem of mode competition in overmoded structures and thus will allow the extension of the operating frequency of the devices to higher frequencies at higher order modes.