磁控管是低能电子直线加速器中的核心部件。近年来，随着低能电子直线加速器日趋小型化，对磁控管的性能参数提出了新的要求。在X波段，脉冲功率高于1.5MW的高占空比磁控管的研制很大程度上影响了该波段低能电子直线加速器的研制和产业化水平。本论文主要围绕研制达到上述要求的同轴磁控管展开，同时对磁控管中关心的理论问题进行了研究。论文通过在三维PIC程序中建立同轴磁控管模型，确定了满足收敛性要求的模拟参数。在此基础上，模拟得到的同轴磁控管工作特性与实验基本吻合，验证了模型的正确性。论文分析了已有磁控管理论模型中对磁控管内电荷分布的描述，同时根据PIC模拟中得到的磁控管内电荷分布，发现已有的理论都不能很好的解释磁控管中轮轭层电荷分布特性，提出了利用等离子体流体理论分析磁控管轮轭内电荷分布的方法，得到了磁控管轮轭层边界的下降沿特性。根据得到的轮轭层电荷分布，提出了两种预测磁控管工作特性的新方法，并做了初步研究。与一般的多腔磁控管不同，同轴磁控管的谐振系统分内腔和外腔两个部分，论文通过对同轴磁控管的模拟和冷测实验研究，分析了其内外腔谐振模式的特点；同时，同轴磁控管中干扰模的抑制方式也存在较大差异，需要通过在合适位置安放衰减瓷的方式对同轴磁控管的干扰模进行衰减，论文通过模拟研究比较了衰减材料的损耗角正切对同轴磁控管起振过程的影响，确定了在清华大学研制的同轴磁控管中，需要选用损耗角正切大于0.01的衰减瓷。清华大学通过研制X波段Ⅰ型同轴磁控管积累了设计、工艺等多方面的经验。论文总结了Ⅰ型磁控管在测试过程中出现的问题，确定了增大阴极面积以降低阴极负荷的改进方案，并结合模拟工具设计了清华大学Ⅱ型同轴磁控管。研制并测试了3只Ⅱ型管样管，其中Ⅱ-2#输出功率达到1.65MW，占空比0.81‰，Ⅱ-3#输出功率1.53MW，占空比0.64‰，达到设计要求。在Ⅱ型磁控管热测实验中得到的P~I曲线与模拟结果相吻合，这为今后借助PIC模拟进行磁控管设计奠定了基础。

Magnetrons are the key components of low energy linear accelerators. In recent years, the increasingly compact design of the low energy linacs requires an X-band pulsed magnetron with reliable performance of 1.5 MW peak power and high duty factor. In this dissertation, we focus on the development of a coaxial magnetron that meets these requirements; in addition, we address the issues regarding the space charge distribution in the magnetron.We modeled the coaxial magnetron in the 3D PIC code MAGIC. The simulation parameters were tuned according to our studies in numerical convergence. We conducted simulation study of the performance chart of a TypeⅠcoaxial magnetron developed at Tsinghua University. Good agreements are found when the simulation results are compared against the experimental results, which verified our simulation model.We likewise reviewed several theoretical models of the space charge distribution in magnetrons, and compared them against our PIC simulation results. We found that the Brillioun’s theory is effective in obtaining the height and density of the hub, yet encounters difficulties when explaining the charge density at the edge of the hub layer due to the pressumption of single particle motions in the Brillioun’s theory. Therefore, we developed a new model to analyze the space charge distribution in the hub layer with the plasma fluid theory. Meanwhile, we discussed two new approaches to obtain the performance of the magnetron in this dissertation.The mode features of the coaxial magnetron are analyzed utilizing the EM simulations, as well as cold test experiment. PIC simulations are applied to obtain the oscillating process of the magnetron. We found the magnetron would work properly when the loss tangent of the attenuator exceeds 0.010, yet fails to work otherwise. Hence, we concluded that attenuators with loss tangent exceeding 0.010 are required for the coaxial magnetrons. In addition, we obtained the quality factors of the working mode and N/2-1 mode in the coaxial magnetron with various attenuators. Our work indicated that the N/2-1 mode is effectively absorbed if the loss tangent of attenuators exceeds 0.010, which also agrees with the PIC simulation results. Moreover, we summarized the problems during our construction and high-power test of the type Ⅰ coaxial magnetron developed at Tsinghua university previously. We modified the design to decrease the cathode loading in the coaxial magnetron, then constructed and tested three tubes with the modified design. The output power and duty factor of the Ⅱ-2# magnetron achieve 1.65 MW and 0.81‰, while that of the Ⅱ-3# magnetron are 1.53MW and 0.64‰, respectively. The P~I curve of Ⅱ-2# and Ⅱ-3# magnetrons are compared against the PIC simulation results, and good agreements are found which verifies our simulation model.