金属-铁电陶瓷沿面阴极重频发射特性研究

The high-frame-rate flash x-rays generators with at least tens kHz are very important dignosis equipments on material eject,explosive mechanics,gas eject dynamics,space debris domain,whose key point is cathode capable of electron emission at desirable high repetitive rate.So,for the sake of explore whether it is feasible to design a high-frame-rate flash x-rays generator by way of the metal-ferroelectric flashover cathode,it is essential to study high-frame-rate electron emission charateristics of the cathode. . Many researchers lucabrate low-frame-rate cathode's continuous emission in uniform field, However little concern high-frame-rate cathode's multi-shoots emission in ununiform field.Ferroelectric ceramic has extreme minim vapor at explosive electron emission,furtherly,by mechanism of associating expolsive emission with vacuum flashover,metal-ferroelectric ceramic could decrease evidently shot limen to get uniform distributing plasma,and reduce material evaporation to realize low vapor pressure,meanwhile avoid some high temperature spots on cathode surface which impossibly come back to appropriate value between pulse intervals. Metal-ferroelectric cathode can get high repetition because of these merits.To realize high-frame-rate emission cathode,researchers must study how cathode's plasma arise and expand on metal-ferroelectric ceramic surface in extremely ununiform electric field,understand the process of the cathode and tube's hold-voltage resume,comprehend the factors with relate to insulating resume.Oherwise,by getting the metal-ferroelectric cathode's emission charateristics,and make knowledge of the cathode's emission theories, we can establish cathode's electron emission and voltage-current model,that's available to design high-frame-rate flash x-rays generators.

在研究材料的微喷物理过程、电磁套筒内爆界面形变、航空发动机燃油喷射规律等科学问题时，迫切需要数十kHz以上猝发高重频闪光X光机进行多幅照相以认识动态过程。其中具有高重频发射能力的阴极是实现高重频X光机的技术基础。.迄今国内外对均匀电场下平面阴极连续低频发射特性研究较多，但极少研究不均匀场中阴极猝发高重频发射特性。本课题基于同轴圆片阴极X光二极管提出圆环片状和圆环锯齿状金属-铁电陶瓷沿面阴极，通过研究其三相点电场分布探索降低其发射阈值和产生均匀初始等离子体的方法；采用高速摄影手段研究在极不均匀电场下等离子体在该阴极表面发展的规律，探索实现发射均匀等离子体的方法；研究阴极等离子体扩散复合过程，阴极结构参数和材料种类，制备工艺与绝缘恢复过程关系，探索实现高重频发射阴极的方法；通过实验研究该阴极在重频下的电流发射特性，深入理解其重频发射物理机制，为基于该阴极实现重频X光机提供理论基础。

基于200kV重复频率光导开关型脉冲功率源和工业X光二极管开展了金属-陶瓷沿面阴极重频发射特性研究。提出一种轮辐状金属-陶瓷沿面阴极，采用三维电场分析表明陶瓷介电常数、陶瓷孔径是影响其三相点电场的主要因素，实验表明在相同结构参数下，基于该阴极的二极管电流约为金属阴极的2倍，功率脉宽内二极管阻抗下降率约为金属阴极的1/3，ICCD图像表明其发射十分均匀；基于优化结构的轮辐阴极实现了200 kV电压1 kHz帧率2猝发脉冲闪光X射线，两个脉冲的功率、X射线信号及耦合至二极管的能量基本一致。