Weakly charged round micro-plasma jet flows into vacuum

Abstract

This paper presents a model for highly dilute microplasma jet flows expanding into a vacuum from a round exit, with given number density, bulk velocity, temperature, and potential at the exit. The Debye length at the exit is assumed to be large, the quasi-neutral condition is adopted to treat charges, and the potential field is computed with the Boltzmann relation. At farfield, the exit degenerates as a point source, and simplified analytical formulas for the density, velocity, temperatures, potential, and electric field components are obtained. From the crucial centerline properties, exact but more compact solutions are further developed. The treatment is based on the gas kinetic theory, and the results are analytical and generic. The results include rich physics and offer insights into better understanding of many existing models in the literature, for example, the cosine law plume model shall be used with caution. The current results can be widely applicable to estimate the whole flow and potential fields, with reduced simulation and measurement costs. Farfield property estimations can be performed without numerical simulations and measurements. Based on these results from this work, more advanced models may be further developed.

Geometrically self-similar ion acceleration in collisionless plasma beam expansion

“…We include a Monte Carlo collision (MCC) model, which simulates the collisions between beam ions with a background neutral gas, into the PIC model discussed in section 2. We apply an analytical free molecular solution for the spatial distribution of neutrals [39,40] to calculate the neutral gas background in the vacuum chamber. The density and velocity of the background neutrals are given as:…”

A Simple Gas-Kinetic Model for Dilute and Weakly Charged Plasma Micro-Jet Flows

“…As such, sub-grid modeling work on the jet end and plume flows must be done to resolve this issue. A recent paper [12] has reported the development of such an axisymmetric model, and the purpose of this paper is to complete the counterpart model for a two-dimensional flow scenario. The fundamental assumptions are still the exit speeds are very high, and the local potential changes are very mild.…”

“…In the end, we want to explain the relations between this paper and another recently published paper [12]. Both focus on highly dilute slightly charged jet out of an exit; this paper is scenario from a planar exit, and the other is the scenario from a planar exit.…”

“…Both focus on highly dilute slightly charged jet out of an exit; this paper is scenario from a planar exit, and the other is the scenario from a planar exit. The latter [12] includes more details and can aid readers understand the work. For highly dilute neutral gaseous jets out of an exit, there are another two past papers [8,9] which can help understand the work presented in this work-the first one is from a planar exit, and the other is from a round exit.…”