中文摘要：

高亮度同步辐射光源和自由电子激光对直线加速器的耦合结构的性能提出了更高的要求。通常的单边耦合器由于耦合腔结构的不对称导致腔内电磁场的不对称性，较大地影响了束流的品质。本文介绍一种新的加载介质棒的单边耦合器，结构简单、易于加工。由优化模拟结果可知：新型耦合器中的电场的二极分量和四极分量的场振幅梯度分别为-0.0794%和-0.0666% , 而传统的单边耦合器二极和四极场振幅梯度分别为5.02%和2.99%，有效地减弱场振幅的不对称性。另外, 本文对耦合器做了详细的结构分析计算：温度场分布、热变形、热应力, 结果表明新型耦合器与通常的单边耦合器的热性能差别不大，说明新型耦合器有望用于提高光源性能。

英文摘要：

High brightness synchrotron radiation light source and free electron laser （ FEL ） have higher requirements on the performance of linear accelerator coupling structure. The traditional single-side couplers induce asymmetry of electromagnetic fields in cavity due to the asymmetry of cavity structure, which greatly affects the beam quality. A new type of single-side coupler loaded with dielectric cylindrical rods is proposed. Its structure is simple, and easy to be processed. The simulation results show that dipolar and quadrupolar electric field amplitude gradient for the new coupler are -0.0794% and -0.066~, respectively, but the ones are 5.02%, 2.99% for the traditional couplers. The asymmetry of field amplitude is effectively weakened. The temperature field distribution, thermal deformation and thermal stress of coupler are analyzed and calculated. Results show that the new coupler has little difference with the usual single-side coupler in thermal performance, and is expected to improve the performance of light source.