Design and experiment of long-pulse C-band relativistic backward wave oscillator
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摘要: 从抑制强场击穿的角度出发，结合传统理论和相关粒子模拟方法，设计并优化了工作于C波段的长脉冲相对论返波管。模拟中，利用强流相对论电子束的空间电荷场效应，将3 GW功率水平下电动力学结构表面的最大发射电场控制在700 kV/cm以下。利用实验室700L脉冲功率驱动源平台开展了相关实验验证，实验结果表明，通过合理的结构设计，在功率3 GW级水平下，C波段相对论返波管中的脉冲缩短问题能够得到有效抑制。实验中，当工作电压760 kV、电流为9.0 kA时，在4.23 GHz频点处获得的输出微波功率为2.8 GW，微波脉冲半高宽约101 ns，功率转换效率约41%，实验结果与模拟结果吻合较好。Abstract: Increasing the single pulse energy is always one of the development targets in high power microwave (HPM) domain. Pulse shortening should be emphatically focused on and solved. Combining the classical theory and particle-in-cell simulation, a long-pulse C-band relativistic backward wave oscillator (RBWO) was designed and optimized. Using the space charge effect of the intense relativistic electron beam, the maximum field strength on the electrodynamic structure surface was no more than 700 kV/cm with about 3 GW output. Further, the related experiment was carried out based on the 700L high voltage pulse generator in our laboratory. As demonstrated by the studies, pulse shortening of the RBWO can be effectively suppressed at about 3 GW level through rational design. With a 760 keV, 9.0 kA beam in the experiment, a 2.8 GW, 4.23 GHz microwave was obtained in the far-field measurement. The pulse width was about 101 ns and the device efficiency was 41%. The experimental result agrees well with that obtained in the simulation.
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图 1 矩形腔结构和梯形腔结构场形比较
Figure 1. Field comparison of rectangular cavity and trapezoidal cavity
图 4 产生微波功率随时间的变化及微波频谱
Figure 4. Variation of output power with time and the frequency spectrum
图 5 长脉冲RBWO谐振反射器、慢波结构和提取腔内表面典型电场分布
Figure 5. Typical electric field distribution in the reflector, SWSs and extractor of the long-pulse RBWO
图 6 典型辐射场检波波形和高速示波器采集的典型微波波形
Figure 6. Typical demodulated microwave signal and undemodulated microwave signal
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