周期加速结构单通带色散曲线的研究

Analysis of Single-Passband Dispersion Curves in Periodical Accelerating Structures

提出一种新的分析周期加速结构的方法 (腔模法 ) .它首先利用有限元等方法计算出单个加速腔内的电短路和磁短路模式 ,然后构造出闭模和开模 ,把耦合腔中的单通带电磁场展开为开模和闭模的线性叠加 ,再结合耦合孔处开模对应的能通量 ,经过数学变换后就得到整个结构的单通带色散曲线 .

The cavity mode method presented in this paper is used for analysis of the dispersion curves in periodical accelerating structures. At first,we computed the electromagnetic fields in a single cavity with the finite element method and construct the normalized orthogonalized short and open modes. Then it is assumed that the fields in the whole structure can be expanded linearly with these modes. Considering the Maxwell equations and the periodical boundary conditions,we get the relationship between the frequencies and the phase shifts. The parameters in the equation can be computed with the short and open modes. For the example of the disk loaded waveguide shown in this paper,it is very easy to obtain the single passband dispersion curves. The accuracy can reach 10 -6 . The method can also be used to compute the high order modes that meet the requirement of the single passband.