一种磁控管用W-Y合金阴极热发射特性研究

Thermionic Emission Characteristics of Novel W-Y Alloy Cathode of High-Power Magnetron Tube

研制了一种大功率磁控管用W-Y合金阴极,并对该合金阴极的热发射、寿命等特性分别进行了测试。热发射测试结果显示,该合金阴极在1400℃工作温度时,其直流热发射特性曲线出现了较明显的空间电荷偏离点。而当阴极工作温度升高为1500℃、1600℃时,该阴极的直流热发射特性曲线一直呈直线上升,并未出现空间电荷偏离点,这与金属阴极的热发射特性曲线一般会出现空间电荷偏离点常识相违背。寿命测试结果显示,该合金阴极在1600℃工作温度下,经过80 h寿命测试后,热发射电流密度从初始的1.5直线下降至0.2 A/cm^2,能谱仪分析结果显示,此时W-Y合金阴极中Y元素从初始的46.45%下降至8.36%。最后,对该合金阴极热发射反常现象机理进行了有益的探讨。

A novel type of the W-Y cathode,compressing W-filament surface-modified with W-Y alloy coating synthesized via powder metallurgy,has been developed for the high power magnetron tube. The impact of the W-Y coatings on the DC thermionic emission characteristics and lifetime of the new cathode was investigated with scanning electron microscopy and energy dispersive spectroscopy. The preliminary results show that the well-defined space charge deviation point at 1400℃,as regularly observed in the thermionic emission curves of all conventional metal cathodes,vanished at 1500℃ and/or 1600℃,possibly because of the Y evaporation and because of the plasma layer formation near the W-Y alloy surfaces. T ested at 1600℃ for 80 h,the emission current density decreased from 1. 5 down to 0. 2 A/cm^2,accompanied by a Y-content reduction from 46. 45% to 8. 36% in the W-Y alloy coating.