为了得到场约束方式下，金属陶瓷封装端窗透射微型X光管发射电流的最大化和焦斑尺寸的最小化，对热阴极发射体的几何结构进行仿真计算，为设计实物模型提供技术方案。首先，从理论上推导了直热式阴极发射体、发射电流密度与几何结构的关系，其次讨论了有限积分算法在求解电场分布数值解过程中的离散化思路，最后利用CST粒子工作室软件，建立了几何模型，对阴极发射体的几何结构进行了优化。在灯丝距离控制极0.4 mm、控制极开孔直径为0.6 mm的位置，能够得到较小的焦斑和较高的电荷密度分布。试制的阴极发射体最大发射电流可达85 μA。

In order to get optimization results of the emission current and the focal spot size of the micro X-ray tube, the geometric structure of the cathode emitter is simulated. Firstly, the relationship among the direct thermal cathode emitter, the emission current density and the geometry structure is derived theoretically. Secondly, the discretization of the finite integral algorithm in solving the numerical solution of the electric field distribution is discussed. Finally, the geometric model is built by using the CST particle Studio software, and the geometric structure of the cathode emitter is optimized. When the distance between the filament and the control pole is 0.4 mm, and at the position the aperture diameter of the control pole is 0.6 mm, smaller focal spot and higher charge density distribution are attainable. The emitter fabricated has a maximum emission current of 85 μA.