同轴慢波结构相对论高功率微波产生器理论分析

 推导了同轴波导的空间电荷限制流，其值大于圆波导的空间电荷限制流。因此在阴极电势和束流相等的情况下，同轴波导中的束流具有更高的动能，同轴器件有可能获得更高的微波转换效率。理论推导出同轴慢波结构中考虑束流空间电荷影响的色散方程，利用Matlab进行了编程求解。不考虑束流空间电荷影响时，编程计算结果与Superfish模拟结果一致。由考虑束流空间电荷影响的色散方程数值计算结果，可知文献中提出的同轴慢波结构相对论高功率微波产生器工作在准TEM模的π模，频率为7.67 GHz，峰值时间增长率较高，电子束损失的能量与其初始能量之比为34%。这些结果均与文献中的数值模拟结果一致。同时理论分析说明该种器件无论在能量转换效率，还是在产生微波脉冲的上升时间上均具有优势。

Analytic theory of relativistic high power microwave generator with coaxial slow wave structure

In this paper, a linear theory is presented of a relativistic high power microwave generator with coaxial slow wave structure. The space-charge-limiting current of a coaxial cylindrical waveguide is derived, which is larger than that of a hollow cylindrical waveguide. Thus, the electron beam in the former has more kinetic energy than that in the latter when the cathode potential and the current are the same and the coaxial device might obtain higher beam-wave conversion efficiency. Also derived is the dispersion relation for a coaxial cylindrical waveguide with sinusoidally varying wall radii. For the case of dispersion relation without considering the beam space charge effect, the theoretical results agree very well with the simulation results with Superfish. According to the numerical solutions to the dispersion equation considering the beam space charge effect, the operating mode of the generator is n point of quasi-TEM mode and the frequency is 7.67 GHz in which the high peak growth rate correspondingly occurs and the energy conversion efficiency is 34%. These results calculated by the analytic theory are close to those obtained by PIC simulation and reveal the advantages of high efficiency and short microwave pulse risetime for the generator.