开放式圆柱光栅周期结构的色散特性分析

STUDY ON OPEN COLUMN SLOW-WAVE GRATING STRUCTURE’S DISPERSION CHARACTERISTICS

研究了一种新的开放式圆柱光栅周期结构,该结构可以作为Smith-Purcell自由电子激光和相对论行波管中的慢波结构.采用近似的场论方法,用一系列相连的矩形阶梯来近似代替光栅上任意槽形的槽的连续轮廓,利用各阶梯面上导纳的匹配,以及槽与互作用区的连续和匹配条件,获得了任意形状槽圆柱光栅周期结构的色散方程,并讨论了系统结构参数变化对系统色散特性的影响.利用软件MAGIC对结构的色散特性进行了二维模拟,与理论计算得到的值符合良好.

The open column slow-wave grating structure, which is a novel type slow-wave system for Smith-Purcell FEL and relativistic TWT, was presented. The dispersion equation of the structure was derived by means of an approximate field-theory analysis, in which the continuous profile of the groove was approximately replaced by a series of rectangular steps, and the field continuity at the interface of two neighboring steps and the matching conditions at the interface between the groove region and central region were employed. The dispersion characteristics of the fundamental wave were numerically calculated and the effects of the geometrical dimensions of the grating on dispersion characteristics of system were also analyzed. And the simulation values of the structure, which is performed by using two-dimensional particle-in-cell code MAGIC, match the theoretical values very well.