Approximate semi-analytical solutions for the steady-state expansion of a contactor plasma

Abstract

We study the steady-state expansion of a collisionless, electrostatic, quasi-neutral plasma plume into vacuum, with a fluid model. We analyze approximate semi-analytical solutions, that can be used in lieu of much more expensive numerical solutions. In particular, we focus on the earlier studies presented in Parks and Katz (1979 (Pasadena, CA)). By calculating the error with respect to the numerical solution, we can judge the range of validity for each solution. Moreover, we introduce a generalization of earlier models that has a wider range of applicability, in terms of plasma injection profiles. We conclude by showing a straightforward way to extend the discussed solutions to the case of a plasma plume injected with non-null azimuthal velocity.

On electron boundary conditions in PIC plasma thruster plume simulations

“…Extensive numerical efforts devoted to the characterization of the properties of plasma thruster plumes can be found in the literature; see, for example, references [16][17][18][19][20] and those cited in [15,21]. The treatment of electrons varies from kinetic (solving Vlasov-Boltzmann directly or using the Particle-in-Cell (PIC) method [22]) to fluid approximations that rely on an isothermal or polytropic closure of the equations.…”

Plasma expansion towards an electrically insulated surface

“…Given the dimensionless scaling in our formulation, these substantial surface effects may be relevant to a variety of plasma systems of different scales, including solarwind interaction with airless bodies (Rhodes & Farrell 2019), laboratory inertial fusion (True 1981;Sack & Schamel 1987) or plasma contactors (Camporeale et al 2015).…”

“…Note that, for application to the lunar wake problem, this dynamic model must be adjusted to the steady-state surface condition. Other applications of plasma expansion theory, such as laboratory inertial fusion (True 1981;Sack & Schamel 1987) or plasma contactors (Camporeale, Hogan & MacDonald 2015), may also find relevance in this general dimensionless model.…”