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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。
Preparation of scandium oxide doped tungsten powder by spray drying method. Using this kind of tungsten powder to make the matrix and impregnating barium aluminate and calcium, a high current density scandium diffused cathode was developed. The pulse and DC emission performance and lifetime of the cathode were studied in flat-panel diode and electron gun, and the effects of electron cooling and temperature compensation at high DC current density were discussed. The results show that the cathode current density in the diode structure can reach 122 A / cm ~ 2 and the DC current density can reach 60 A / cm ~ 2 when the temperature is 950 ℃. The life test was carried out under the condition of the initial DC load of 20 A / cm ~ 2, the current gradually increased to 30 A / cm ~ 2 and the continuous operation for 2000 h increased the current density to 40 A / cm ~ 2. h above. In the electron gun, the knee temperature was only 900 ℃ for the under-heating characteristic at the initial pulse current of 58 A / cm ~ 2, and the cathode was stable for 1000 h at a current density of 50 A / cm ~ 2 and still continued. The above results show that the developed cathodes are superior to the other types of hot cathodes currently used, and the process is controllable. The cathodes are capable of practical application in new continuous-wave microwave vacuum electronic devices such as the terahertz field.