【作者】 周恒；

【导师】 舒挺； 李志强；

【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】 磁绝缘线振荡器（MILO）是一种性能优异的正交场吉瓦级高功率微波（HPM）源，是当前HPM领域研究的热点之一。MILO阻抗一般比较低（~10），负载电流比较大，而过大的电流容易导致负载区阳极等离子体的产生。为此，希望通过提高MILO的阻抗来降低电流、提高器件效率、改善以及拓宽MILO的应用。本文从理论分析、数值模拟和实验三个方面对高阻MILO进行了较为细致的研究，得到了一些有价值的结果，这为MILO的重频和长脉冲运行奠定了基础。理论分析方面。基于顺位流模型得到了磁绝缘电流。为了提高MILO功率效率的上限，需要降低负载电流与总电流比值，可以通过减小同轴二极管阻抗或增大平板二极管阻抗来降低该比值，为了保证磁绝缘，同时还需要相应提高工作电压。利用顺位流理论，得到了MILO的阻抗与阴阳极半径之比及与电压之间的关系，为数值模拟中提高MILO的阻抗提供了指导。数值模拟方面。与负载限制型MILO相比，锥形MILO在功率效率方面更有潜力，据此选定锥形MILO作为器件的基本结构。通过冷腔分析得到了MILO谐振模式的场分布、谐振频率和腔体Q值等基本的谐振特性。用PIC方法得到MILO阻抗与阴阳极半径之比及与电压之间的关系。对于给定模型，当阴阳极半径之比在2.1~3.1范围内增大时，MILO阻抗在23.5~32.4范围内相应提高；电压在560~940kV范围内增大时，MILO的阻抗在28.2~30.7范围内缓慢增大。在保证MILO正常工作的前提下，分析并得到了以下结论：频率越低，则阻抗上限越大；阻抗越高，则最优功率效率对应的电压越高。在优化过程中，综合利用以下手段来提高MILO的功率效率：阻抗和频率的选取、磁绝缘状态的调试、电子发射区起点和终点位置的调整，以及微波的提取和反馈的优化。典型模拟结果如下：20的MILO，在675kV、33.4kA条件下，输出微波功率为4.2GW，频率为2.45GHz，功率效率为18.0%；30的MILO，在810kV、26.9kA条件下，输出微波功率为5.5GW，频率为1.74GHz，功率效率为25.3%；45的MILO，在1.16MV、25.8kA条件下，输出微波功率为6.9GW，频率为580MHz，功率效率为23.1%。为了验证高阻MILO的可行性，本课题开展了相关的实验研究。基于20MILO的优化结果，设计加工了实验装置。典型实验结果如下：在电压665kV、电流32.3kA条件下，微波辐射功率为1GW，频率为2.59GHz，辐射模式为TM01。最后，分析了实验过程中导致高阻MILO阴极烧蚀、频率漂移、功率偏低的原因和并给出了相应的解决办法更多还原

【Abstract】 Magnetically insulated transmission line oscillator (MILO) is an excellent crossedfield device designed specifically to generate microwave power at the gigawatt level，which is a major hotspot in the field of high-power microwave (HPM) research at thepresent time. At present, the impedance of MILO is relatively low（~10）. As a result,the load current is quite large, which limits the further development and application ofMILO. On one hand, the anode plasma formation in the load region could result in thesevere pulse shortening and electrode erosion. On the other hand, intensive space chargeeffect could result in the relatively lower power conversion efficiency. Based on thisbackground, increasing the impedance of MILO can help to overcome these weaknesses.These research results also found a firm foundation for the design of the long-pulseMILO with repetitive operation. By the use of theoretical analysis, particle simulation,and experimental measurement, the high impedance MILO has been investigatedsystematically. A series of valuable results have been obtained.Firstly, according to the parapotential model, the magnetically insulated currentwas obtained. In order to increase the power conversion efficiency of MILO, the ratio ofload current-to-anode current should be decreased. Several methods could be used:increasing the side area of the cathode, decreasing the area of the cathode end,decreasing the distance between the side face of the cathode to the slow wave structure,increasing the distance between the cathode end and the electron collector, andincreasing the diode voltage. Based on the theory of parapotential flow, the influencelaw of both the ratio of cathode radius-to-anode radius and the diode voltage on theMILO impedance were studied, which provides efficient guidance for increasing theMILO impedance.Secondly, the tapered MILO was chosen as the basic structure, which could obtainhigher power conversion efficiency by comparison with the load-limited MILO. Thefield distribution of the resonance mode, the resonance frequency, and the quality factorare acquired. By employing a2.5-dimensional PIC code, the relation of MILOimpedance to both the ratio of cathode radius-to-anode radius and the diode voltagewere obtained numerically. It was found that for a given structure, within the range of2.1-3.1, the increase of the ratio of cathode radius-to-anode radius could increase theimpedance of MILO within the range of23.5-32.4; It was also found that theimpedance of MILO increased slowly with the range of28.2-30.7when the diodevoltage increased within the range of560-940kV. It was found that the lower thefrequency of MILO, the greater the upper limit of the MILO impedance. And further,the higher the impedance of MILO, the higher the diode voltage corresponding to themaximal power conversion efficiency. All associated factors were considered to increase the power conversion efficiency of the MILO during the optimizing prose, such as thechoice of impedance and frequency, the adjustment of magnetically insulated state, thechoice of the position of the electron emission area, and the optimization of theextraction and feedback of the microwave. The representative numerical results were asfollows. For the20MILO, the microwave output power was4.2GW with the initialelectron energy of675keV and the electron beam current of23.3kA. The microwavefrequency was2.5GHz. The beam-to-microwave power conversion efficiency was18.0%. For the30MILO, the microwave output power was5.5GW with the initialelectron energy of810keV and the electron beam current of26.9kA. The microwavefrequency was1.7GHz. The beam-to-microwave power conversion efficiency was25.3%. For the44MILO, the microwave output power was6.3GW with the initialelectron energy of1.1MeV and the electron beam current of25.0kA. The microwavefrequency was630MHz. The beam-to-microwave power conversion efficiency was22.7%.Finally, correlative experiments were carried out to verify the feasibility of the highimpedance MILO. The experimental study has been performed on the optimized20MILO designed with the help of simulation. The representative experimental resultswere as follows. When the voltage was665kV and the current was32.3kA, amicrowave was generated with power of1GW, mode of TM01and frequency of2.60GHz. Furthermore, the reason for the frequency drift, cathode erosion and lowpower conversion efficiency were investigated experimentally. Based on this, feasiblesolutions are given.更多还原