【作者】 柴斌；

【导师】 张世昌；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2011， 博士

【摘要】 回旋自谐振脉塞(Cycoltron Autoresonance Maser,缩写CARM)是一类基于电子回旋谐振辐射的高功率电磁波源。自CARM的概念被提出以来,由于其独特的工作特性(如所需工作磁场低,RF结构的横向尺寸大,可采用弱相对论电子束等)而引起人们的广泛关注。尽管过去各国学者对CARM已经进行过大量的理论研究,但大部分工作只针对于CARM中的单模束波互作用,而对多模束波互作用的研究则少有涉及。然而,当CARM的工作频率延伸至太赫兹(THz)或亚THz频段时,通常需要采用高阶的电磁波模式来增加器件的几何尺寸,以解决器件的机械加工和散热问题。这必然导致波导腔体中电磁波模式的过模问题,从而诱发器件工作时出现模式竞争,所以,对工作于THz或亚THz频段的CARM器件来讲,对其进行多模束波互作用的理论研究显得很有必要。为此,针对目前CARM多模理论研究的相对匮乏的现状,本文以CARM放大器为研究对象,通过对已有单模非线性理论的总结和分析,建立了比较完善的CARM多模非线性理论,并利用多模理论详细研究了工作于THz频段的CARM器件中各电磁模式与相对论电子束的互作用过程。全文主要工作包括：第一章：绪论。简单介绍了回旋自谐振脉塞的工作原理以及国内外对于回旋自谐振脉塞的研究现状；第二章：推导了同轴波导CARM中TE模式和TM模式电磁波的束波耦合方程以及圆柱波导中TE模式和TM模式电磁波的束波耦合方程,同时给出了考虑波导壁欧姆损耗后的束波耦合方程以及相对论电子在多电磁波模式共同作用下的电子运动方程,从而得到了完整描述CARM多模束波互作用的自洽非线性方程组；第三章：介绍了CARM多模束波互作用非线性模拟软件的设计方法,对软件设计中涉及到的关键问题进行了详细的阐述,如物理量的归一化、初值的选取以及方程组数值求解过程中的精度监测等,最后,给出了整个模拟软件设计的流程图,并利用FORTRAN语言编制了数值模拟软件。利用本模拟软件不仅可以对CARM中的整个多模束波互作用过程进行数值模拟,同时还可以对CARM的工作参数进行优化设计；第四章：从实验(利用国际上已公布的实验数据)和理论两方面对本论文所编制的多模束波互作用非线性模拟软件进行了可靠性验证,为下一步太赫兹CARM器件多模非线性模拟结果的正确性提供了保障；第五章：利用本文CARM多模非线性理论模型对采用高阶横电(TE)工作模式的太赫兹CARM进行了多模束波互作用非线性数值模拟。通过进一步分析主要工作参数对多模束波互作用过程的影响发现,高阶TE模式太赫兹CARM器件的性能对工作参数具有很强的依赖性,因此在参数设计过程中有必要对其进行多模束波互作用模拟分析；第六章：利用本文CARM多模非线性理论模型对采用高阶横磁(TM)工作模式的太赫兹CARM进行了多模束波互作用非线性数值模拟,证实了太赫兹CARM采用高阶TM模式的可行性和有效性,并通过进一步分析主要工作参数对多模束波互作用过程的影响发现,高阶TM模式太赫兹CARM器件的性能对工作参数具有很强的依赖性,因此在参数设计过程中有必要对其进行多模束波互作用模拟分析；本文所建立的CARM多模非线性理论以及所编制的模拟软件,可以对CARM中多电磁模式与相对论电子束的互作用过程进行数值模拟,通过进一步分析工作参数对多模束波互作用过程的影响,可以发现潜在的模式竞争,能够对高工作频率(如太赫兹或亚太赫兹频段)、高阶工作模式CARM器件的参数设计和优化提供一定的帮助。更多还原

【Abstract】 Cyclotron autoresonance maser (CARM) is a kind of high power electromagnetic wave sources, the operating mechanism of which is based on the electron cyclotron resonance radiation. Since the concept of CARM was proposed, it has been attracting much attention due to its prospective peculiarities such as relatively lower operating magnetic field, larger RF cross-sectional size, and weak relativistic electron beam). Although plenty of theoretical models have been performed for CARM in the past years, most of them mainly focused on the interaction of a single mode with the electron beam, and relatively less attention was paid to the multimode interaction. As the frequency of a CARM is stretched to terahertz (THz) or sub-THz wave ranges, higher-order mode is always adopted so as to enlarge the cross-sectional dimension of the cavity and then to facilitate the mechanic manufacture and thermal wall loading. However, it may also lead to severe over-modes and thus mode competition may happen. Consequently, multi-mode interaction should be considered in a THz or sub-THz CARM. Based on the single mode nonlinear model, a multimode nonlinear theory is proposed for CARM and the nonlinear interaction of multimodes with relativistic electron beam in a terahertz CARM is specially analyzed. The main work of this thesis includes:In Chapter 1, the operating principle and recent development of CARM are briefly introduced.In Chapter 2, a complete set of self-consistent equations describing the nonlinear interaction of multimodes with the relativistic electron beam in CARM is derived. These equations include the beam-wave coupling equations for TE mode coaxial CARM, TM mode coaxial CARM, TE mode cylindrical CARM, TM mode cylindrical CARM. The beam-wave coupling equations taking Ohmic losses into account and the motion equations for electron immerged in multimode electromagnetic waves are also derived.In Chapter 3, the key issues of computer code for the proposed multimode nonlinear theory are introduced, including normalization of quantities, choice of initial parameters, accuracy monitoring. Finally, the block diagram of software is presented and the computer codes are programmed in FORTRAN language. These codes can be employed for both the simulation of the whole interaction process of multimodes with the relativistic electron beam and the optimization of operating parameters.In Chapter 4, the multimode nonlinear theory and computer code are verified by the comparison of experimental and theoretical results which have been published. These verifications ensure the reliability of the results simulated in the next Chapters.In Chapter 5, a THz, high-order TE-mode CARM is analyzed by multimode nonlinear theory. The influences of operating parameters on multimode beam-wave interaction indicate that the performance of a high-order TE mode CARM deeply depend on the operating parameters, and thus it is necessary to perform multimode beam-wave interaction for parameter design.In Chapter 6, a THz, high-order TM-mode CARM is analyzed by multimode nonlinear theory. The feasibility of a THz CARM operated with TM mode is verified. The influences of operating parameters on multimode beam-wave interaction indicate that the performance of a high-order TM mode CARM deeply depend on the operating parameters, and thus it is necessary to perform multimode beam-wave interaction for parameter design.The proposed multimode nonlinear theory and computer codes can be employed to analyze the interaction of multimodes with relativistic electron beam in CARM. In addition, the potential mode competition in CARM can also be revealed by observing the influence of operating parameters on multimode beam-wave interaction and this will be benefit to the design and optimization of CARM operating parameters.更多还原