场发射X射线管电子光学系统的设计和研究

Design and Simulation of Novel Field Emission X-Ray Tube Electron Optical System

设计了一种基于场发射阵列阴极的X射线管结构。制备了金属尖锥阵列场发射阴极,结果表明该阴极具有良好的电子发射能力和稳定性,在阳极电压为3400 V的条件下,发射电流达1.46 mA,电流密度达516.4 mA/cm^2,适合应用于X射线管中。利用CST粒子工作室仿真软件对X射线管的电子光学系统进行计算,得到了可行的结构方案,结构由阵列阴极、聚焦极和阳极组成,阴极与聚焦极等电位,该结构中阴极面积为10 mm×2 mm,总发射电流约为10 mA,满足X射线管的发射要求。阳极电子束斑大小为1 mm×1 mm,可得到有效焦点大小为0.58 mm×1 mm的X射线。研究为进一步制造高分辨率的场发射X射线管打下了基础。

Herein,we reportedthedevelopment of X-ray tube electron optical system. First, a Mo-tip field emission array cathode without grid electrodes was fabricated. At 3400 V, the emission current and current density were 1.46 mA and 516. 4 mA/cm2 , respectively, Next, the X-ray tube electron optical system, comprising the emission array cathode,focusing electrode and anode,was modeled and simulated with software CST particle studio for design optimization. The simulated results show that novel Mo-tipfield emission array was a reliable electron source for the X-ray tube. For example,the optimized electron optical system has the electric field of 4.7 V/μm （ the onset field of 3 V/μm） ,cathode area of 10 mm×2 mm,and total emission current of l0 mA. Finally,the X-ray emission was evaluated. Irradiating at 30°, the 1 mm× 1 mm emission electron beam generated an X-ray effective focal spot of 0. 58 mm× 1 ram,satisfying the requirements of X-ray tube.