W波段同轴波导回旋行波管放大器的稳定性研究

推导出了考虑损耗层厚度影响的有限电导率材料加载同轴波导中横电模传输常数的解析表达式。结合同轴波导回旋行波管的非线性理论对分布损耗涂层加载的W波段TE₀₂模同轴波导回旋行波管的互作用系统进行了稳定性研究, 分析了互作用系统中的不稳定问题。研究表明:互作用电路各区 (线性、非线性区) 长度的变化不但会导致互作用系统最危险竞争模式的变化, 还会导致竞争模式的局部轴向模发生转移, 合理选择互作用段的长度是稳定工作模式的重要条件;相比普通圆波导结构, 采用同轴波导结构, 稀释了工作模式附近的模式密度, 并通过分布损耗加载, 提高了竟争模式起振电流, 相应地提高了工作模式的稳定性。基于稳定性分析结果, 在电压60 kV、电流13 A、电子注速度零散为3%的情况下, W波段同轴波导回旋行波管放大器可获得峰值功率232 kW, -3 dB带宽2.5 GHz的放大性能。

Stability of W-Band Coaxial-Waveguide Gyrotron Traveling-Wave Tube: A Simulation Study

Herein, we addressed the stability of coaxial-waveguide gyrotron traveling-wave tube (TWT) with distributed wall losses.The effect of the lossy layer thickness on the stability of W-band TE₀₂ mode coaxial-waveguide gyro-TWT was mathematically modeled, theoretically analyzed and numerically simulated.The simulated results show that the lengths of linear/nonlinear interaction sections have a major impact.For instance, the lengths are responsible for the change of the most risky competing mode and for the shift of local axial oscillation of competing mode.So the optimized section-lengths stabilize the interaction.Moreover, when it comes to stability, the coaxial waveguide outperforms the conventional circular waveguide because it rarefies the mode spectrum and reduces the neighboring modes competition.For a 60 kV and a 13 A electron-beam with velocity-spread of 3%, the newly-designed W-band coaxial waveguide gyrotron amplifier had a peak power of 232 kW and-3 dB bandwidth of 2.5 GHz.