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利用Fourier级数展开法,给出了任意几何结构的表达式的求解方法.通过数值计算,对比分析了余弦、梯形和矩形波纹慢波结构(slow-wave structure,SWS)的色散特性.根据S参数理论,研究了这三种SWS纵向模式选择的特性,提出了在同轴慢波器件中加入同轴引出结构,可减少所需SWS周期数,不但使器件结构更为紧凑,还可避免纵模竞争从而提高器件效率、稳定产生微波频率.进一步通过KARAT2.5维全电磁粒子模拟程序,探讨了分别采用三种SWS的相对论返波振荡器(backward-wave oscillator,BWO)的束-波作用的物理过程,设计了一种紧凑型、吉瓦级、同轴L波段BWO,分析了不同形状SWS的选取原则.在此基础上,开展了初步实验研究:在二极管电压为670kV,电子束流为10.7kA,引导磁场为0.75T的条件下,输出微波峰值功率约为1.02GW,微波波形半高宽为22ns,功率转换效率约为14.2%,频率为1.61GHz.
The Fourier series expansions method is used to solve the expression of arbitrary geometric structure. The dispersion characteristics of cosine, trapezoid and rectangular wave slow-wave structure (SWS) are analyzed by numerical calculation. According to S Parameter theory, the characteristics of these three kinds of SWS longitudinal modes are studied, and the coaxial lead-out structure is proposed in the coaxial slow-wave device to reduce the number of required SWS cycles, which not only makes the device structure more compact but also avoids vertical Mode competition so as to improve the efficiency of the device and generate the microwave frequency stably.Through the KARAT2.5 dimensional full-scale electromagnetic particle simulation program, the beam-wave effects of the relativistic back-wave oscillator (BWO) , A compact, gigabit-class, coaxial L-band BWO was designed and the principle of selection of SWS with different shapes was analyzed. Based on this, a preliminary experimental study was carried out. At a diode voltage of 670 kV and electron beam current Is 10.7kA, and the guidance magnetic field is 0.75T, the peak power of microwave output is about 1.02GW, the FWHM of microwave is 22ns, the power conversion efficiency is about 14.2% and the frequency is 1.61GHz.