Plasma generation in a long, narrow, metal tube by electron beam injection

We describe our investigations of the current distribution in a non-self-sustained hollow-cathode glow discharge in a long metal tube. The discharge is initiated and sustained by injecting an electron beam generated by a forevacuum-pressure plasma–cathode electron source into the tube. It is shown that the distribution of discharge current along the inner sidewall over the tube length and, correspondingly, the distribution of plasma density along the tube depend primarily on tube geometry and electron beam current. The character of the discharge current distribution is determined by the ratio of contributions to ionization by beam electrons and by secondary electrons emitted from the tube bottom (if the lower end of the tube is closed) and from the tube sidewall. These processes may lead to a non-monotonic distribution of discharge current with a minimum in the middle. Increasing the discharge current levels out this minimum, improving the uniformity of the current distribution over the tube length.

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Characterization of transversely confined electron beam-generated plasma using two-dimensional particle-in-cell simulations

Cao,

Chen,

Sun

et al. 2023

Physics of Plasmas

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Electron beam-generated plasmas (EBPs) have been used to modify the surface properties. In certain applications, EBPs are transversely confined and their properties are of value to the treatment. In this paper, the characteristics of an electron beam-generated argon plasma, confined within a narrow gap, are investigated using a two-dimensional particle-in-cell simulation. The employed particle-in-cell/Monte Carlo collision model accounts for the electron and ion kinetics, as well as collisions between electrons and the background gas, including the elastic scattering, excitation, and impact ionization. Our simulations reveal a strong correlation between the plasma density and the beam density within the plasma bulk. The excitation of obliquely growing waves is observed, which is found to have a significant impact on the transport of beam electrons, thereby leading to the non-uniformities of plasma density and electron temperature. Specifically, the obliquely growing waves increase the local plasma density while reducing the electron temperature. These contrasting effects compensate for each other, and therefore, to some extent, smooth out the distributions of ion flux and energy flux. We further examine the variations of plasma parameters with respect to the beam current density, beam energy, and gas pressure. Increasing the beam current density or decreasing the beam energy results in higher plasma density and electron temperature, while increasing pressure leads to a higher plasma density but electron temperature scarcely changes. Based on the simulation results, we propose an approach to achieve independent control of the ion flux and energy flux by adjusting beam current density, beam energy, and pressure.

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Plasma generation in a long, narrow, metal tube by electron beam injection

Cited by 5 publications

References 15 publications

Specific features of focused electron beam transport through a narrow metal tube at negative potential in the forevacuum pressure range

Specific features of focused electron beam transport through a narrow metal tube at negative potential in the forevacuum pressure range

Discharge in a long metal tube with an electron beam generated by a forevacuum plasma–cathode electron source

Characterization of transversely confined electron beam-generated plasma using two-dimensional particle-in-cell simulations

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