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Analysis of arc-cathode system from in-situ diagnostics of tungsten electrode during operation

从钨电极运行过程中的原位诊断分析电弧阴极系统

基本信息

批准号：
16360365
负责人：
TANAKA Manabu
金额：
$ 7.49万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360365/
关键词：
Arc Tungsten electrode Thermionic cathode Work function Laser system In-situ measurement Emitter materials Content その場測定光電効果

项目摘要

An in-situ measurement of electrode work functions in gas tungsten arcs during operation has been carried out in order to analyze complex phenomena in arc-cathode system. This technique is based on the photoelectric effect occurring at the surface of a tungsten cathode with the use of a pulse laser system consisting of a Nd-YAG laser and a dye laser. Three types of tungsten electrode, namely, pure W, W-2% ThO_2 and W-2% La2O_3 were used in this project. The gas tungsten arcs were operated in argon at atmospheric pressure at a current of 200 A. The effective work functions of pure W, W-2% ThO_2 and W-2% La_2O_3 electrodes during operation were found to be, respectively, 4.6, 2.8 and 3.0 eV from in-situ measurements. These results were very close to the work functions of W, ThO_2 and La_2O_3 obtained from the literature.Furthermore, four types of tungsten electrode, namely, pure W, W-0.5% La2O_3, W-1% La2O_3 and W-2% La2O_3 were additionally used. The effective work function clearly decreased with increase of La2O_3 content of tungsten electrode, which showed the same tendency with the tip temperature.These experimental results of effective work function of cathode were given to a unified arc-electrodes model to take into account the close interaction between arc plasma and thermionic cathode. Calculations were made for predictions of current attachment at the thermionic cathode with different electron emitter materials at a current of 200 A in argon gas tungsten arc with a water-cooled copper anode. Theoretical results were compared with experimental results in current attachment area, shape of self-stabilized arc and surface temperature of cathode. It was concluded that the current attachment at thermionic cathode was dependent on work function, melting point and Richardson constant of emitter materials.

为了分析钨极电弧-阴极系统中的复杂现象，对钨极电弧工作过程中的电极功函数进行了现场测量。该技术是基于使用由Nd-YAG激光器和染料激光器组成的脉冲激光系统在钨阴极表面发生的光电效应。本课题采用纯W、W-2%ThO_2和W-2%La_2O_3三种钨电极。气体钨电弧在氩气中在大气压下以200 A的电流操作。由现场测量得到纯W、W-2%ThO_2和W-2%La_2O_3电极在工作时的有效功函数分别为4.6，2.8和3.0eV。此外，还添加了纯W、W-0.5%La_2O_3、W-1%La_2O_3和W-2%La_2O_3四种钨电极。随着钨电极中La_2O_3含量的增加，阴极的有效功函数明显减小，且与电极尖端温度的变化趋势一致.计算了水冷铜阳极氩气钨弧中200 A电流下不同电子发射体材料的热离子阴极上的电流附着预测。在电流附着面积、自稳弧形状和阴极表面温度等方面与实验结果进行了比较。结果表明，阴极电流附着与发射体材料的功函数、熔点和Richardson常数有关。