粒度调控对钨阴极表面发射微区的影响

The influence of particle size control on emission micro-area oftungsten cathode surface

摘要:

为了在微米尺度探究未分级钨粉、分级钨粉制备钨基体在阴极热电子发射性能上的差异，深入了解阴极表面微区电子发射过程和阴极发射机理，本文采用新型深紫外激光发射电子显微镜/热发射电子显微镜系统（DUV-PEEM/TEEM）对两种钨粉制备的阴极表面进行了光电子、热电子成像分析。结果显示，与未分级钨粉相比，分级钨粉制备钨基体的显微组织更加均匀，且闭孔率由1.44%降至0.47%；光电子+热电子联合成像精确得出两种阴极的发射均主要集中于孔隙及孔隙中的活性物质上；通过热电子图像对比及分析，分级钨粉制备阴极的热电子发射微区面积更大、分布更均匀；且在1050℃工作条件下，分级钨粉制备阴极的脉冲电流密度为30.79A/cm2，发射斜率为1.38；综合分析显示其具备更理想的本征热电子发射能力和发射均匀性，这对于了解阴极发射性能及改善热阴极制备工艺有一定的指导作用。

关键词:热阴极;深紫外激光;光发射电子显微镜;热发射电子显微镜;电子发射;

Abstract:

In order to research the cathodic thermionic emission performance difference between preparation of tungsten matrix used ungraded tungsten powder and graded tungsten powder on the micron scale, and to gain a deeper understanding of the electron emission process of the cathode surface micro-area and the cathode emission mechanism, a newly developed instrument aiming at meeting the special operation requirements of thermal dispenser cathode is used in this paper. This instrument called DUV-PEEM/TEEM combines the functions of deep ultraviolet laser photo-emission electron microscope and thermal-emission electron microscope. Thanks to the powerful functions of DUV-PEEM/TEEM, the photoelectron and thermoelectron image of prepared cathode from two tungsten powders was analyzed. The results showed that compared with the ungraded material tungsten powder, the microstructure of the tungsten matrix prepared by the graded tungsten powder is more uniform, and the closed cell ratio was reduced from 1.44% to 0.47%; the photoelectron and thermionic united imaging accurately showed that the emission of the two cathodes mainly located at the pores and active substances of pores; via thermal electron (TEEM) images, the thermal electron emission micro-area area of the cathode prepared by graded tungsten powder was larger and the distribution was more uniform than the cathode prepared by ungraded tungsten powder; and under the working condition of 1050℃, the pulse current density of the cathode prepared by graded tungsten powder was 30.79A/cm2, and the emission slope was 1.38, comprehensive analysis showed that it had more ideal intrinsic thermionic emission capability and emission uniformity, which has a certain guiding effect on understanding the cathode emission performance and improving the hot cathode preparation process.

Key words:thermal cathode; deep ultraviolet laser; light emission electron microscopy; thermal emission electron microscopy; electron emission