采用谐波工作的回旋管互作用磁场比基波磁场降低了1/s，可降低整管磁场设计难度，具有较大的应用前景。通过对W 波段二次谐波回旋行波管高频介质加载结构、模式竞争和注波互作用研究，确定了该放大器的工作参数。非线性模拟表明，当应用100 kV，20 A，α=1.2 的电子注时，该回旋管可在91 GHz 频率处产生465 kW 的输出功率和49 dB 的增益结果。并且，基于耦合波理论，讨论了一个轴对称半径微扰的TE02~TE01 输出模式变换器，效率在95%以上时，其带宽达到4 GHz。

Harmonic operation is of special significance due to its low magnetic field operation, and the magnetic field of the s th harmonics gyrotron at a given frequency is reduced by a factor of s for operation. By using an interaction circuit with dielectric loaded, the operating parameters of the W band TE02 mode second harmonic gyrotron Traveling-Wave Tube(gyro-TWT) amplifier are determined by analysis of dielectric loaded, mode competition and interaction between electron beam and wave. Nonlinear analysis shows that the amplifier can generate a saturated peak power of 465 kW with a gain of 49 dB at 91 GHz when utilizing a 100 kV, 20 A, α=1.2 electron beam. Based on coupled mode theory, a TE02-TE01 mode converter within a tapered waveguide radius is discussed and a bandwidth about 4 GHz is obtained when the conversion efficiency exceeds 95%.回