Abstract
Self-oscillations of non-neutral plasma diode operating in the anode-glow mode are analysed using the self-consistent one-dimensional Particle-in-Cell Monte Carlo collisions model. In order to obtain these states, the current exceeding the space-charge limited current has to be emitted from the cathode, the electron mean free path must be much longer than the cathode-anode gap, and the cathode voltage must be slightly larger than the ionization potential of the background gas. It is obtained that in such a case, immobile ions form the electrostatic trap for the electrons generated in the cathode-anode gap. These electrons oscillate between the cathode and the anode causing the self-oscillations of the plasma potential. It is shown that the increase of the emission current leads to the increase of the frequency of the obtained self-oscillations. Starting at some value of the emission current, a lot of the emitted electrons are got trapped in the electrostatic well, which leads to the transition to chaos.
Highlights
Discharges driven by electron emission from the walls have long history [1] and are of interest for many applications such as electric propulsion, plasma etching, high-power microwaves generation etc. [2]
The emission current was varied in the range 21-110 A/m2, which, as it follows from the Child-Langmuir law, exceeds the vacuum space-charge limiting current of the considered diode
The analysis has shown that the diode selfoscillations are obtained if the following three conditions are satisfied: 1) the space-charge limiting current is emitted from the cathode; 2) the electron mean free path is much longer than the cathode-anode gap; and 3) the cathode potential only slightly exceeds the ionization potential of the background gas
Summary
Discharges driven by electron emission from the walls have long history [1] and are of interest for many applications such as electric propulsion, plasma etching, high-power microwaves generation etc. [2]. Discharges driven by electron emission from the walls have long history [1] and are of interest for many applications such as electric propulsion, plasma etching, high-power microwaves generation etc. The type of discharge depends on the electron emission mechanism. The interest to discharges ignited by thermionic electron emission was driven by arc discharges [3]. Later, these discharges have found their application for thermionic energy conversion to electricity. [4] During the last three decades, a lot of research is devoted to the studies of microwaves generation from diodes with the electron emission from the walls [5,6,7]. Thermionic emission drives more complex setups for diamond film deposition, [8] or hollow
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