喷雾干燥纳米氧化钪粒子掺杂含钪扩散阴极的发射特性

Emission Characteristics of Ba-W Dispenser Cathode Doped with Spray-Dried Nano-Sized Scandia

采用喷雾干燥法制备氧化钪掺杂钨粉。用这种钨粉制作基体并浸渍铝酸钡、钙,研制了大电流密度含钪扩散阴极。分别在平板二极管和电子枪内研究了阴极的脉冲与直流发射性能以及寿命,并对高直流电流密度下的电子冷却效应和温度补偿进行了探讨。结果表明,阴极在二极管结构内,温度为950℃时,空间电荷限制区偏离点脉冲电流密度可达到122 A/cm^2,直流电流密度可达到60 A/cm^2以上。在初始直流载荷20 A/cm^2的条件下进行寿命试验,电流逐步上升至30 A/cm^2,连续工作2000 h,提升电流密度至40 A/cm^2后,继续稳定工作达3000 h以上。在电子枪内,初始脉冲电流58 A/cm^2时的欠热特性膝点温度仅为900℃,阴极在50 A/cm^2的电流密度下稳定工作1000 h,并仍在继续。上述结果表明,所研制的阴极优于当前所用的其他各类热阴极,工艺可控,具有在太赫兹领域等新型连续波微波真空电子器件内实际应用的能力。

A novel type of Ba-W dispenser cathodewas fabricatedby spray-drying of W pellets,pre-doped with nano-sized scandia（ Sc2O3） and impregnated in Ba-and Ca-aluminates. The impact of the fabrication conditions on the microstructures and emission properties of the novel dispenser cathode was investigated with scanning electron microscopy. The tested results show that the new highly porous,Sc2O3-doped cathode outperforms the conventional ones fabricated by solid-liquid reaction and sol-gel techniques because of its better performance and longer lifetime.To be specific,at 950℃,thespace charge limited DC current density,in closely-spaced diodes,was over 60 A/cm^2,after temperature compensation for electron cooling; and the stable DC current density of 30 A/cm^2 at 950℃ had lasted for longer than 3000 h. In Pierce electron-gun tests,initiated at 58 A/cm^2,the knee-point temperature was900℃ and the cathode worked fairly well for over 1000 h with a pulsed current density of 50 A/cm^2.