Gyrotrons operating at low voltage are highly attractive for subterahertz applications because such an operation can greatly reduce the size and cost of gyrotron systems. Among the oscillator versions of gyrotrons, the gyrotron backward-wave oscillator (gyro-BWO) features continuous frequency tuning in a broadband. This study investigates the characteristics of the beam-wave interaction in a low-voltage gyro-BWO in the subterahertz wave range. Operation at lower voltages has the advantage of a broader frequency tuning range and the suppression of negative $k_{z}$ competing modes. The phenomenon of a sharp increase in the start-oscillation current near the lower limit of the operating voltage is investigated. In addition to the linear characteristics, the dependence of the efficiency and tuning bandwidth on voltage is analyzed. The potential performance of a low-voltage gyro-BWO is predicted using the existing beam parameters: beam voltage of 2 kV, beam current of 0.2 A with a velocity ratio of 1.0, and axial velocity spread of 20%. Although the gyro-BWO operating at 2 kV exhibits the problem of low efficiency (an efficiency of 5.6%), it has a broad frequency tuning range of 3.0 GHz. The efficiency can be enhanced to 15% (a peak power of 60 W) by tapering the waveguide radius. Possible competing modes in low-voltage operation are considered and a stability analysis reveals stable operation.

中文翻译：

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兆赫兹范围内低压回旋振荡器的线性和非线性特性

在太赫兹应用中，低压操作的回旋管极具吸引力，因为这样的操作可以大大减小回旋管系统的尺寸和成本。在回旋振荡器的振荡器版本中，回旋振荡器反向波振荡器（gyro-BWO）具有宽带中的连续频率调谐功能。这项研究调查了在太赫兹波范围内的低压陀螺-BWO中束波相互作用的特性。在较低电压下运行的优势在于，频率调谐范围更广，并且抑制了负电压。 $ k_ {z} $ 竞争模式。研究了接近工作电压下限的启动振荡电流急剧增加的现象。除了线性特性，还分析了效率和调谐带宽对电压的依赖性。使用现有的射束参数可预测低压陀螺-BWO的潜在性能：射束电压为2 kV，射束电流为0.2 A，速度比为1.0，轴向速度扩展为20％。尽管以2 kV工作的gyro-BWO表现出效率低（效率为5.6％）的问题，但它具有3.0 GHz的宽频率调谐范围。通过减小波导半径可以将效率提高到15％（峰值功率为60 W）。考虑了低压运行中可能存在的竞争模式，而稳定性分析表明运行稳定。