【作者】 曹亦兵；

【导师】 张建德； 贺军涛；

【作者基本信息】 国防科学技术大学 ， 电子科学与技术， 2012， 博士

【摘要】 发展更高功率、更高频率和更长脉冲的高功率微波设备始终是高功率微波研究领域的重要课题。在基于渡越辐射效应的高功率微波发生器中，渡越时间振荡器因为简单紧凑的结构一直广受关注，但其在高功率和长脉冲运行方面存在困难，这主要受限于传统渡越时间振荡器中易于产生等离子体的导体箔结构。相对论速调管取消了导体箔，是一种有望高功率、长脉冲运行的渡越器件，然而其较长的漂移段加剧了强流相对论电子束发生传输不稳定性的风险，同时对励磁系统也提出了更高的要求。此外，在向更高频率发展的过程中，因为缩小的腔体尺寸，渡越时间振荡器和相对论速调管本身功率容量进一步减小，高功率和长脉冲运行遇到更大困难。为了顺应高功率微波源的发展趋势，本课题提出并研究了基于渡越辐射效应的新型无箔高功率微波发生器。新器件相对于速调管结构更为紧凑，仅需要较低的外加导引磁场，同时具有高功率、高频率和长脉冲运行的潜在优势。本文从理论分析、粒子模拟和实验研究等方面对新型器件进行了较为系统的研究，确立了新型渡越器件的研究基础。首先，利用模式匹配理论求解了新型渡越腔结构中的调制场分布。数值计算结果证实了新型结构中的调制场呈现准体波分布特性。从单腔渡越腔结构的场分布特性出发，推导得到了表征任意数目腔体结构中调制场与电子束发生能量交换的电子束归一化电导函数，由电导函数可以得到对应结构的工作电压范围。其次，论文对比研究了L波段渡越器件的模拟和实验结果。在二极管电压620kV、电流25kA、导引磁场0.5T的条件下，实验得到了约3.5GW的输出微波功率，微波频率1.64GHz，器件效率达到22.6%。实验结果与粒子模拟结果几乎一致。初步实验证实了新型器件的高功率输出能力，同时也发现了其在长脉冲运行方面存在的诸多不足，为进一步的结构改进提供了依据。对新型渡越器件的结构改进主要在X波段进行。从二极管间隙宽度、电子束收集位置、器件表面射频场强等方面全面考虑了改进型结构长脉冲运行的可能性。在束压710kV、束流14.5kA、导引磁场0.8T的条件下，粒子模拟得到了2.5GW的输出微波功率，主频为9.38GHz，效率约24.3%。器件内部表面轴向射频场强控制在590kV/cm左右，低于真空中射频击穿场强阈值。基于改进型渡越器件的设计，对其进行了初步的实验研究。在电子束束压780kV、束流13.5kA、导引磁场约0.8T的条件下，初步实验得到了约1.1GW的输出微波功率，主频9.34GHz，器件效率约10.5%。实验结果与相同工作电压电流波形下的粒子模拟结果(~1.5GW)吻合较好。初步实验也表明改进型渡越器件具备长脉冲运行的潜力，为下一步的长脉冲实验奠定了基础。最后，考虑到未来的应用需求，对新型渡越器件进行了进一步的拓展研究。在产生多频段微波辐射方面，新型结构表现出了许多新的优势。在电子束压500kV、束流15kA、导引磁场0.8T的条件下，粒子模拟得到了总功率约2.37GW的双频段微波输出，效率达到31.6%。在锁频锁相方面，初步研究表明：低功率注入时(~MW)，同一射频信号控制下的多个同频渡越器件之间的相位锁定是可能的；高功率注入时(~100MW)，新型渡越器件的频率和相位能被外部信号有效锁定。更多还原

【Abstract】 To generate high power microwave (HPM) with higher power, higher frequencyand longer pulse width is always one of the hottest topics in the HPM domain. In theHPM generators based on transit radiation, the transit-time oscillator (TTO) is attractivebecause of its simplicity and compactness, yet it is very difficult to realize high-poweredand long-pulsed operation, which has been greatly limited by the conducting foilstructures. Without foils structure, the relativistic klystron is expected to operate at highpower and long-pulse. However, due to a long drift-tube, the intense relativistic electronbeam (IREB) would probably degrade in its transportation process, and the externalmagnetic field is also required more strictly. Besides, in pursuit of higher frequency,owing to the reduced dimensions, both the devices are confronted with the limititationof power capacity.Because of these reasons, a novel foilless HPM generator based on transit radiationis put forward. With a low external guiding magnetic field, such a device is morecompact than the klystron and has the advantages of high output power, high operationfrequency and long-pulsed operation. In the paper, the proposed device is systematicallyinvestigated by theoretical analysis, particle-in-cell (PIC) simulation and experiments,and its investigation foundation is eventually established.Firstly, the modulating field distributions are analytically solved by using modematching method. The numerical calculation shows that the modulating fields in thestructure have the trait of quasi body wave. From the field distribution of the singlecavity, the normalized beam-loading conductance ratio of the multi-cavity structure,indicating the beam-wave energy interchange, is derived. Consequently, the operatingvoltage range can be easily obtained.Secondly, the simulation and experimental results from the L-band device arecompared. With a620keV,25kA electron beam guided by an external magnetic fieldof0.5T, a3.5GW microwave at1.64GHz is obtained and the corresponding efficiencyreaches22.6%. The experimental results are almost consistent with those of the PICsimulation. The initial investigation testifies that the novel device is capable ofgenerating high output power. Simultaneously, it also indicates that the designed devicehas many shortcomings in the long-pulsed operation, which can provide a good guidefor the next structure improvement.Further, an improved device based on transition radiation is designed at X-band. Inorder to realize long-pulsed operation, special attentions are focused on thecathode-anode gap, the distance between the extractor and the electron collector, and theaxial electric field strength on the structure surface. With a710keV,14.5kA electronbeam guided by an external magnetic field of0.8T, a2.5GW microwave at9.38GHz is obtained in the simulation, and the corresponding efficiency is about24.3%. Thehighest axial electric field strength on the surface of electrodynamic structure is only590kV/cm, which is lower than the RF breakdown threshold in vacuum.Based on the PIC simulation, the elementary experiment of the improved X-banddevice is carried out in our laboratory. With a780kV,13.5kA electron beam guided byan external magnetic field of~0.8T, a9.34GHz,1.1GW microwave has beenexperimentally obtained and the corresponding efficiency is about10.5%. The resultsare basically consistent with those obtained in the simulation with the similar beamparameters (~1.5GW). The elementary investigations indicate that the improved deviceis hopeful of long-pulsed operation, which has laid a good foundation for the cominglong-pulsed experiments.Finally, considering the realistic demands, studies of the novel device are furtherwidened to the multi-frequency and phase-locking domains. In the generation ofmulti-frequency HPM, the novel structure shows many merits. With a500kV,15kAelectron beam guided by an external magnetic field of0.8T, a dual-frequency HPM hasbeen obtained in the simulation. The output power is about2.37GW and thecorresponding efficiency reaches31.6%. In the phase-locking, preliminary studies haveshown that, phase-locking among several devices with the same operation frequency ispossible when the input RF power is relatively low (~MW), and the operation frequencyand phase can be effectively controlled by the external signal when the input RF powergets to100MW.更多还原