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热阴极的电子初速分布问题过去研究得很多,如对纯金属阴极和复杂阴极的电子初速分布,及在直流发射情况下和脉冲发射情况下工作时的电子初速分布都进行过细致的研究。 但是在电子温度高于、低于还是等于阴极温度(晶体点阵温度)和在什么情况下速度分布是连续的,在什么情况下速度是不连续的,研究结果并不一致。因此,我们在前人的工作基础上,进一步明确这些问题。 实验是在直接减速和先加速后再减速的情况下以及在直流发射和脉冲发射情况下进行的,得到的结果是: (1)直接减速时,由于支取的电流小,电子温度与阴极温度一致。 (2)对氧化物阴极来说,在直流发射情况下,特别是在空间电荷限制的情况下,电子初速分布是麦克斯韦分布;而只有在脉冲情况下,电子初速才能分布成谱。 (3)电子温度高于阴极温度,即所谓电子气过热,主要是由于涂层电阻,而速度谱线的出现则是涂层电阻和涂层表面不平的联合作用。
In the past, there have been many studies on the electron velocity distribution of hot cathodes, such as the electron first-rate distribution of pure-metal cathodes and complex cathodes, and the electron velocity distribution in the case of direct-current emission and pulsed emission. However, the results are inconsistent when the electron temperature is higher than, lower than or equal to the cathode temperature (crystal lattice temperature) and under what conditions the velocity distribution is continuous and the speed under which the velocity is discontinuous. Therefore, we further clarify these issues on the basis of our predecessors’ work. The experiment was carried out under the conditions of direct deceleration and acceleration after first acceleration and deceleration under direct current and pulsed emission. The results obtained are as follows: (1) In direct deceleration, the electron temperature is consistent with the cathode temperature due to the small current drawn, . (2) For the oxide cathode, in the case of DC emission, especially in the case of space charge limitation, the electron velocity profile is Maxwellian distribution; and only in the case of impulse, the electron velocity can be distributed into the spectrum. (3) The electron temperature is higher than the cathode temperature, the so-called electron gas overheating, mainly due to the coating resistance, and the appearance of the speed spectrum is the combined effect of the coating resistance and the coating surface unevenness.