Research progresses on Cherenkov and transit-time high-power microwave (HPM) sources in National University of Defense Technology (NUDT) of China are presented. The research issues are focused on the following aspects. The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed. The compact coaxial relativistic backward-wave oscillators (RBWOs) at low bands are developed. The power efficiency in M-Type HPM tubes without guiding magnetic field increased. The power capacities and power efficiencies in the triaxial klystron amplifier (TKA) and relativistic transit-time oscillator (TTO) at higher frequencies increased. In experiments, some exciting results were obtained. The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode. Both L- and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%. There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions. A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%. A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB. A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.

为改善一种L波段磁绝缘线振荡器（MILO）重复频率运行时的真空环境，建立了器件在分子流下的抽气模型，采用Monte-Carlo方法对阴极脉冲放气后的瞬态抽气过程进行了模拟计算，获得了不同时刻气体分子在MILO内部的3维分布情况，并据此提出了一种“分布式”抽气方案，即在MILO靠近气源的微波传输区增加一抽气单元，以缩短脉冲间隔内的抽气时间。在Torch-01调制器上开展了MILO“分布式”抽气的实验验证，结果显示，“分布式”抽气时的气压下降特征时间为单泵的0.22倍，与模拟结果基本一致；初步的重复频率测试也表明“分布式”抽气能够缩短脉冲串间隔内的抽气时间以保持器件运行时的真空水平。在所给实验条件下，从真空的角度，“分布式”抽气能够使MILO有效运行的重复频率数提升至单泵抽气时的5倍。

在对磁绝缘线振荡器(MILO)慢波结构色散特性进行理论分析的基础上,结合负载限制型和渐变型MILO的特点,对X波段MILO慢波结构、阴极和中心阳极进行了设计。利用2.5维全电磁PIC程序进行粒子模拟,研究了输出功率与结构参数之间的关系,进一步优化MILO结构。在外加电压为510 kV,束流43 kA情况下,模拟得到平均功率2.83 GW的微波输出,中心频率为8.2 GHz,功率转换效率12.9%。

利用数值方法计算了磁绝缘线振荡器(MILO)主慢波结构谐振腔和扼流腔的谐振频率和场分布.结果表明:当主慢波结构腔内半径为4.6 cm,扼流腔内半径为4.2 cm,阴极半径为3 cm时,MILO工作在3.6～4.4 GHz频率范围,扼流片可以阻止微波功率向脉冲功率源泄漏,这有利于提高器件微波输出的功率;4.5～4.9 GHz频段为慢波结构的阻带,微波在该频段截止.计算了C波段MILO开放腔的谐振频率,当模式分别为3π/8,π/2,5π/8,3π/4时,其谐振频率分别为3.18,3.76,4.00,4.11 GHz;并通过实验测出了开放腔的谐振频率,其相应的值分别为3.80,3.94,4.08.4.18 GHz,Q分别为194,143,231,468.数值计算的谐振频率与实验测出的频率基本一致.