In harmonic gyrotrons, the narrow operating region of the harmonic mode is significantly restricted by the severe mode competition from the fundamental parasitic modes, which makes it important to study the nonlinear effects of beam-wave interaction in the case of a nonideal electron beam. In this article, the effect of the electron velocity spread and the beam radius spread on the mode excitation, interaction efficiency as well as mode competition are analyzed for the desired harmonic mode and the parasitic fundamental mode operating far from the cut-off frequency. The effect of velocity spread is interpreted via the electron cyclotron resonance condition as well as the electron beam susceptibility with respect to the resonator field. The results show that the velocity spread can greatly broaden the effective operating region of the harmonic mode and the efficiency degradation can be contained at a reasonable level by proper design consideration of the interaction circuit. Whereas, the beam radius spread is the main factor that accounts for the efficiency degradation and can aggregate the mode competition. The results are referential to the design and analysis of harmonic gyrotrons as well as continuously frequency tunable gyrotrons.

中文翻译：

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电子束特性对二次谐波回旋管的影响,电子束特性对二次谐波回旋管的影响

在谐波回旋管中，谐波模式的狭窄工作区域受到来自基本寄生模式的严重模式竞争的显着限制，这使得研究在非理想电子束情况下束波相互作用的非线性效应非常重要。在本文中，针对期望的谐波模式和远离截止频率的寄生基模，分析了电子速度扩展和光束半径扩展对模式激发、相互作用效率以及模式竞争的影响。速度扩散的影响通过电子回旋共振条件以及电子束相对于共振器场的敏感性来解释。结果表明，通过对交互电路进行适当的设计考虑，速度扩展可以极大地拓宽谐波模式的有效工作区域，并且可以将效率下降控制在合理的水平。而波束半径扩展是导致效率下降的主要因素，并且可以聚合模式竞争。研究结果对谐波回旋加速器和连续频率可调回旋加速器的设计和分析具有参考价值。,在谐波回旋管中，谐波模式的狭窄工作区域受到来自基本寄生模式的严重模式竞争的显着限制，这使得研究在非理想电子束情况下束波相互作用的非线性效应非常重要。在本文中，针对期望的谐波模式和远离截止频率的寄生基模，分析了电子速度扩展和光束半径扩展对模式激发、相互作用效率以及模式竞争的影响。速度扩散的影响通过电子回旋共振条件以及电子束相对于共振器场的敏感性来解释。结果表明，通过对交互电路进行适当的设计考虑，速度扩展可以极大地拓宽谐波模式的有效工作区域，并且可以将效率下降控制在合理的水平。而波束半径扩展是导致效率下降的主要因素，并且可以聚合模式竞争。研究结果对谐波回旋加速器和连续频率可调回旋加速器的设计和分析具有参考价值。