爆炸电子发射初期阴极表面电场的研究

摘要

To investigate a complex physical phenomenon and its evolution law at the cathode surface at the initial stage of the explosive electron emission process in a high-power diode, in this paper we present a model of a planar vacuum diode with a field emission cathode. The model is one-dimensional and nonstationary. To study the space charge effect of the emitted electrons on the electric field at the cathode surface, Poisson＇s equation is solved numerically by using our developed code, and the time-dependences of the electric field at the cathode surface for different cases are obtained. The results show that the electric field at the cathode surface first oscillates and finally yields a steady state. The absolute value of the steady electric field at the cathode surface is higher for the higher field enhancement factor at a given applied electric field, and the applied electric field has the same effects on the steady value at a certain field enhancement factor. The electric field at the cathode surface completely determines the extracted field emission current density from the cathode, and at the same time, the electric field at the cathode surface is influenced by the emitting current density.%为了研究二极管爆炸电子发射初始阶段阴极表面复杂的物理现象及规律，建立了由场致电子发射阴极构成的一维平板真空二极管物理模型，通过自行编程数值求解泊松方程，考虑了发射出的电子对阴极表面电场的非线性影响，自洽模拟得到了阴极表面电场随时间的变化情况．模拟结果表明，爆炸电子发射初期，阴极表面电场随时间的增加而呈现出不断振荡的规律，且振荡幅度越来越小，最终到达一个稳态的值，二极管两极板之间的外加电场越大，阴极表面稳态电场的绝对值越大；电场增强系数越大，阴极表面稳态电场的绝对值越大．在整个时间演变过程中，阴极表面的实际电场强度决定着阴极发射的电流密度大小，反过来阴极发射的电流密度又会影响到阴极表面的电场．