【作者】 高梁；

【导师】 钱宝良；

【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】 目前，L、S、C、X波段的相对论返波振荡器已经得到了较为充分的发展，但P波段相对论返波振荡器的实验研究工作尚未见到报导，分析认为P波段较大的结构尺寸是限制其发展的主要原因。同轴相对论返波振荡器的研究及其向低频段的拓展，为实现P波段相对论返波振荡器紧凑化提供了可能，但许多重要的技术问题仍然需要解决。此外，P波段高功率微波还在国防和工业领域具有重要的应用前景。在此背景下，本文综合理论研究、物理分析及粒子模拟结果，提出了一种紧凑型P波段同轴相对论返波振荡器结构，并在实验中成功获得了GW量级P波段高功率微波辐射。本文的研究内容主要包括以下几个方面：（1）研究了同轴慢波结构中的空间电荷限制电流，给出了数值计算结果，并根据数值结果总结出了一种等效分析方法，通过这一方法，可以直观地判断结构参数改变引起的空间电荷限制电流变化情况。推导了任意同轴慢波结构中任意模式的色散方程，并对色散方程进行了数值计算，验证了色散方程在求解色散曲线时的有效性；总结了外波纹同轴慢波结构和双波纹同轴慢波结构中色散曲线随结构参数变化的规律；求解了混合模色散曲线；理论上解释了同轴相对论返波振荡器实验中非对称模式激励的原因。（2）针对普通P波段同轴相对论返波振荡器轴向尺寸大，微波输出饱和慢的缺点，结合数值计算与粒子模拟，对慢波结构进行了详细的物理分析。数值研究指出，双波纹同轴慢波结构较之普通的外波纹同轴慢波结构，能够显著增大同步谐波的耦合阻抗，能够较大地提高时间增长率。因此，选择双波纹同轴慢波结构作为新型器件的慢波结构，并利用线性理论选择了慢波结构参数，预测了器件的工作频率与工作模式。利用粒子模拟方法对慢波结构周期数进行了选择，结果表明当选择三个周期的慢波结构时，器件不仅结构紧凑，而且有较宽的单频工作区间，并在较宽的二极管电压范围内具有较高的束-波转换效率和输出微波功率。最后，基于物理分析，提出了一种紧凑型P波段同轴相对论返波振荡器。（3）对紧凑型P波段同轴相对论返波振荡器进行了粒子模拟优化，在二极管电压585kV、电流7.85kA、导引磁场0.8T的条件下，产生微波功率为1.5GW，效率约为33%，频率为900MHz。模拟结果证明了慢波作用区工作模式为准TEM模，器件工作机制为返波振荡机制。此外，还研究了实验中可进行调节的参数以及加工、装配带来的附加参数对紧凑型器件工作特性的影响。（4）对紧凑型结构进行了拓展研究和结构改进研究。验证了紧凑型P波段同轴相对论返波振荡器设计思想在L波段的可行性，并结合P波段和L波段研究结果，得到了该类器件的相关设计原则。拓展设计了能够在低导引磁场下工作的紧凑型P波段同轴相对论返波振荡器，并设计了永磁导引系统，微波源与永磁导引系统结合的粒子模拟初步证实了永磁封装的可行性。改进了紧凑型结构的收集极，使其有利于长脉冲和重频运行，并提出了一种简单易行的收集极设计方法，避免了使用粒子模拟反复优化，节省了设计时间。改进了紧凑型结构的慢波结构和收集极，提高了器件的效率，在二极管电压585kV、电流7.85kA、导引磁场0.8T条件下，产生微波功率达到2.2GW，效率为48%，频率为900MHz。（5）对紧凑型P波段同轴相对论返波振荡器进行了实验研究。利用薄介质铜阴极获得的典型实验结果如下：在二极管电压570kV、电流8.0kA、导引磁场0.86T、电压脉宽60ns的条件下，产生了功率1.47GW、脉宽40ns、频率897MHz的微波辐射，效率约为32%，实验结果与粒子模拟结果基本一致。此外，利用天鹅绒阴极也获得了与薄介质铜阴极一致的实验结果。研究了二极管电压和导引磁场对产生微波的影响，并在1.2T导引磁场、995kV二极管电压条件下，获得了3.14GW微波输出，效率约为20%，脉冲宽度约47ns。更多还原

【Abstract】 Currently, the relativistic backward wave oscillators (RBWOs) operating in thefrequency regime of L-band, S-band, C-band and X-band have been fully developed, butresearches on the P-band RBWOs are rare. The main reason is that the P-band RBWO is solarge and cumbersome that it is difficult to fabricate and manipulate in experiments.Coaxial RBWO has the potential to realize compactness for the P-band RBWO, but thereare still many important issues to be solved. In addition, the P-band high power microwave(HPM) has the potential applications both in military and industrial areas, and theinvestigation on the P-band RBWO is of importance. Therefore, a compact P-band coaxialRBWO is proposed based on the results of theoretical studies, physical analysis andparticle simulation in this dissertation. Experiments of the compact P-band RBWO arecarried out and a P-band, gigawatt level HPM can be generated effectively. The contents ofthe dissertation are listed as follows.1. Space charge limiting current of a relativistic electron beam propagating in acoaxial slow wave structure (SWS) is derived and calculated. An equivalent analysismethod for investigating the space charge limiting current is given based on the numericalresults. With this method, the effects of the configuration parameters on space chargelimiting current can be determined obviously. The arbitrary mode dispersion equation ofthe coaxial SWS with arbitrary periodic profile is derived and calculated. With thenumerical results, the validity of our dispersion equation for calculating dispersion curve isverified, and the variations of dispersion curve related to the configuration parameters inthe coaxial SWS with only outer conductor ripple and the coaxial SWS with both inner andouter conductor ripple is presented. In addition, the accuracy of the mix mode dispersioncurve is verified and the excitation of the asymmetric-mode in the experiment for thecoaxial RBWO is studied theoretically.2. The large longitudinal dimensions and the long saturation time of the microwavesignal are two main shortcomings for the conventional P-band coaxial RBWO. In order toovercome these shortcomings, the physical analysis on the coaxial SWS is performed withnumerical calculation and particle simulation. Numerical results show that compared withthe conventional coaxial SWS with only outer conductor ripple, the coaxial SWS with bothinner and outer conductor ripples can remarkably enlarge the coupling impedance for the-1st space harmonics of the quasi-TEM and can largely enhance the temporal growth.Therefore, the coaxial SWS with both inner and outer conductor ripples is chosen as theSWS of our novel P-band RBWO. The parameters of the SWS are chosen using the resultsof the linear theoretical analysis, and then the operating frequency and mode of the noveldevice are given theoretically. The SWS period number is chosen by particle simulation. The simulation results show that three periods SWS not only has a compact structure, butalso has a wide region of single-frequency operation and relatively high efficiency andoutput power in a wide range of the diode voltage. Based on the above mentioned analysis,a compact P-band coaxial RBWO is proposed.3. The compact P-band coaxial RBWO is optimized with a2.5-dimension fullelectromagnetic PIC code. With the diode voltage of585kV and the beam current of7.85kA guided by a magnetic field of0.8T, a microwave with frequency of900MHz, powerof1.5GW and efficiency of about33%is obtained. The simulation results also show thatthe operation mode of the device is quasi-TEM mode, and the operating mechanism of thedevice is the mechanism of the backward wave oscillator. In addition, the effects of theadjustable parameters in the experiment and the additional parameters caused by theprocess of the machining and assembling are presented and discussed in detail.4. The extension and improvement studies on the compact P-band coaxial RBWO areperformed. It is demonstrated that the idea of designing a compact P-band coaxial RBWOis also feasibility for the L-band RBWO. A principle of design for the low-band coaxialRBWO is presented with the results of P-band coaxial RBWO and L-band coaxial RBWO.A P-band coaxial RBWO, which can operate at low magnetic field, is proposed and apermanent magnet system is designed for it. The simulation results of the RBWO confirmthe feasibility of permanent magnet, which can be used for the guiding magnetic field. Thecollector of the compact device is improved for the long pulse and repetitive rate operation.Then a collector design method is proposed. The main merit of this method is that it canavoid the use of particle simulation optimization repeatedly, and thus can save time greatly.The SWS and collector of the compact device is improved for increasing the beam-waveconversion efficiency. With the diode voltage of585kV and the beam current of7.85kAguided by a magnetic field of0.8T, the improved device can generate a microwave withfrequency of900MHz, power of2.2GW and efficiency of48%.5. The experiments of the compact P-band coaxial RBWO are performed. Theexperimental results with the dielectric-copper cathode shows that with the diode voltageof570kV and the beam current of8.0kA guided by magnetic field of0.86T, the P-bandmicrowave with frequency of897MHz is obtained. The microwave power is measured tobe1.47GW and the efficiency is approximately32%. The experimental results are in goodagreement with the results of particle simulations. In addition, increasing the guidingmagnetic field to1.2T, a microwave with power of3.14GW, efficiency of20%and pulsewidth of about47ns is obtained at the diode voltage of995kV and the beam current of15.5kA.更多还原