向内发射同轴虚阴极振荡器理论分析与数值模拟

 针对向内发射同轴虚阴极振荡器进行了1维理论分析，给出了电流电压关系的数值解，估算了同轴漂移区空间电荷限制流及虚阴极位置；同时使用MAFIA程序进行了全3维PIC数值模拟研究，通过调节阴极电子发射区与阳极反射板之间距离进行了一系列计算，得到了圆波导中各传输模式频谱及功率。结果表明，尽管使用圆周对称的同轴结构，输出模式中TE₁₁和TM₀₁仍占主导地位，两种模式共同存在，相互竞争。在最佳情况下，当二极管电压为250 kV，电流为20 kA时，得到了微波输出总功率最高为740 MW，功率效率超过10%，主频为3.18 GHz，同时含有较强TE₁₁和TM₀₁模式成分的微波输出。

Theoretical analysis and simulation study on inward-emitting coaxial vircator

One-dimensional theoretical analysis is presented for the inward-emitting coaxial virtual cathode oscillator.Numerical solutions are given for the relationship of the diode voltage and current,the space-charge limited current in the coaxial drift space,and the position of the virtual cathode.Full three-dimensional numerical simulation with the PIC method is carried out using the TS3 module of the MAFIA code.The distance between the cathode emission region and anode reflector is optimized by monitoring the frequency spectrum and output power of the propagating modes in the cylindrical output waveguide.Results show that TE_(11) and TM_(01) modes between them there exists mode competition are both the dominant modes even with the axisymmetric configuration.Based on the previous optimization,the microwave dominant frequency of 3.18 GHz,the total power of 740 MW which contains mainly TE_(11) and TM_(01) modes,are obtained by the numerical simulation when the diode voltage is 250 kV and the current 20 kA.