介质加载复合光栅结构的色散特性研究

提出了一种用于Smith-Purcell器件的介质加载金属光栅周期慢波结构.通过采用本征函数法和单模近似法求解了介质加载金属光栅的"热"色散方程,在同步点得到了注-波互作用的一阶和二阶增长率,分析了光栅槽宽和槽深对色散特性的影响,并研究了电子注参数及其与光栅表面距离等主要参数对增长率特性的影响.结果表明:通过介质加载金属光栅有利于减弱色散,随着介质相对介电常数、槽宽度以及深度的增大,色散曲线变平缓且向低频区移动;当电子注参数变化时,一阶增长率曲线从整体上粗略地描述增长率变化趋势,二阶曲线则更精细地描述增长率相应值的变化.利用软件MAGIC对该结构的色散特性进行了二维模拟,模拟结果与理论计算值符合良好.

Dispersion characteristics of dielectric loaded metal grating

A novel type of slow-wave structure for Smith-Purcell device called dielectric loaded metal grating, is proposed in this article. The “hot” dispersion align of the structure is obtained by using the eigen-function method and single-mode approximation. The first-and second-order growth rate of beam-wave interaction are obtained at the synchronization point. The effects of grating groove width and depth on dispersion characteristic are analyzed, and the influences of electron beam parameters and distance between electron beam and grating surface on growth rate characteristic are also studied. The results show that dielectric-loaded metal grating can effectively weaken the structure dispersion, and that with the increases of relative dielectric permittivity, groove width and depth, the dispersion curve becomes flatter and moves toward low frequency. When the electron beam voltage or current changes, the first-order growth rate curve can only roughly describe the change trend, while the second-order growth rate can accurately show the change values. The simulation of the structure is performed by using two-dimensional particle-in-cell code MAGIC, and the simulation results accord well with the theoretical results.