Development Of 2D Microwave Driven Photonic Crystal Accelerating Structure

In this thesis the design and experimental demonstration of an X-band metallic photonic crystal(PBG structure) travelling wave accelerating structure are presented.The most remarkable property of PBG structure is the photonic band gap. The wave with a frequency inside the band gap cannot propagate into the bulk of the PBG structure. 2D metal PBG structures were introduced to the field of accelerating structure design because they can used to suppress the wakefield in accelerating structure. Wakefields are harmful modes affecting the beam propagation or even destroying the beam. Suppression of wakefields is important.Base on the global band gap diagrams of the metal PBG structure formed by triangular arrays of rods, we derive the condition under which the accelerating mode is confined and the dipole modes can be suppressed. A metallic PBG resonator(X-band) was fabricated with an improved machining technique. The Q-factor of the resonator was 3800, which is much higher than that of the former one.Half of the resonator's outer wall was removed and SiC rods were suggested to be placed at the periphery in order to achieve the HOM damping. According to numerical simulations, the TM11 mode leaks out can be absorbed by absorbers effectively while the influence to TM01 mode is quite little.An X-band travelling wave PBG accelerating structure, including acceleraing cells and couplers, was designed. The group velocity of the accelerating cells is 0.04C to prevent short-range wakefields. Due to PBG structure's character, the coupers's design is more complicated than that of the traditional disk-loaded structure. A quantitative method of coupler simulation which is based on the Kyhl. method was introduced to the PBG structure couplers'design. The locations of some rods between the rectangular waveguide and the center of the coupler were ajusted for tuning and matching and CST Microwave Studio was employed to perform the numerical simulations. A 4-cell metallic travelling wave PBG accelerating structure with couplers was fabricated and experimental results were obtained. The results are basically consistent with the simulations. The SWR of the accelerating mode is about 1.06 near the operating frequency. Further experimental investigations are going to be carried out. This work was supported by the Natural Science Foundation of China (10675116 &1037506).