空心阳极等离子体阴极提取电子束的实验分析

Experimental Analysis of Electron Beam Extracting From a Device with Hollow-anode Vacuum-arc-plasma Cathode

低气压下真空电弧放电产生高电子密度的等离子体,从等离子体中能提取电子束。为了研究一种新型空心阳极-等离子体阴极结构的放电机理,在相同电压和阴阳极间隙下,对新型结构与两平板电极结构进行电弧放电实验,通过测量阴极电压、放电回路电流以及收集极电流来比较两者的特点。结果表明:前者的阴极电位波形在放电开始之后明显低于两平板电极的阴极电位波形,存在明显的电位下垂现象;同时收集极电流在放电回路电流不大时呈现出只有负半波情况。从真空电弧放电机理具体分析解释了收集极电流呈半波的原因,同时采用等效电路模型和等效电位函数对阴极电位下垂做了详细的分析,认为是阳极附近聚集大量电子,因此有未被补偿的负空间电荷,形成电位梯度较大的阻极电位降,电弧等离子体近似为电中性,导致阴极电位下降。

At a low residual gas pressure the vacuum arc produces high electron density plasmas, which can be used to form an electron beam source. In this paper, an experimental research on the discharge mechanisma of a novel hollow anode plasma cathode structure is conducted. At the same voltage and the same distance between anode and cathode, the discharge experiments on the novel structure and two-planar electrodes are carried out and the characteristics of the two structures are generalized by comparing the cathode voltage, discharge loop current（arc current） and collector current waveforms. It can be concluded that there is a cathode potential droop in the novel structure, and the collector current waveform is like a half-sine and lower than zero most of the time. The half-sine phenomenon is analyzed in detail based on vacuum arc discharge mechanism, and the equivalent circuit model and equivalent potential function serve as an interpretation for cathode potential droop. It is proposed that massive concentration of electrons around anode corresponds to incompensated negative space charges, which induce sharp potential drop at anode and newtral arc plasma, and cathode potential drop.