减小直线加速器耦合腔中不对称性的方法

Reducing the asymmetry in coupled cavity of linear accelerator

随着高能物理的发展,特别是大型对撞机、FEL和高亮度同步辐射光源,均对直线加速器的性能提出了更高的要求。单边耦合器结构的不对称性破坏了耦合腔中场的对称性分布,降低了束流的品质。为了改善不对称性,利用CST微波工作室模拟设计了X波段偏心耦合器、双对称耦合器以及介质棒加载耦合器,并对腔中场分布的均匀性进行了分析,而且进行了粒子跟踪。计算结果表明采用新方法设计的加载介质棒耦合器耦合腔中场分布的对称性较好。粒子束团通过该种耦合器和一段加速结构后,束团的分布几乎完全处在束流孔中心,而且束流能散有明显改善。

Background： With the development of high energy physics, high performance of electron linear accelerator is required for large coUider, FEL and high brightness synchrotron radiation light source. Structure asymmetry of single coupler destroys the symmetry of field distribution in coupled cavity, which reduces the quality of beam. Purpose： Optimize the asymmetry of field distribution in coupled cavity and improve the quality of beam. Methods： The simulation designs are made for single offset coupler, double symmetry coupler and the new coupler loaded by dielectric rods at X band by using CST microwave studio code. Results： The results show that the distribution of field in coupled cavity is better and all particles almost locate at the center of beam hole after beam passing through the coupler loaded by dielectric rods. The energy spread has also been significantly improved. Conclusions： The coupler loaded by dielectric rods can optimize the asymmetry of field distribution in coupled cavity and improve the quality of beam.