A non-neutral regime of radio-frequency atmospheric pressure plasma jets: Simulation and modeling

TL;DR

This paper investigates a non-neutral regime in RF atmospheric pressure plasma jets, revealing a drift-soliton-like electron structure through simulation and analytical modeling, challenging the traditional quasi-neutral plasma assumption.

Contribution

It introduces a hybrid kinetic-fluid simulation and an analytical model to describe non-neutral electron structures in RF plasma jets, which differ from conventional plasma models.

Findings

Identification of drift-soliton-like electron structures

Good agreement between simulation and analytical models

Stability analysis of the non-neutral regime

Abstract

Radio-frequency-driven atmospheric pressure plasma jets (RF APPJs) play an essential role in many technological applications. This work studies the characteristics of these discharges in the so-called non-neutral regime where the conventional structure of a quasi-neutral bulk and an electron depleted sheath does not develop, and the electrons are instead organized in a drift-soliton-like structure that never reaches quasi-neutrality. A hybrid particle-in-cell/Monte Carlo collisions (PIC/MCC) simulation is set up, which combines a fully kinetic electron model via the PIC/MCC algorithm with a drift-diffusion model for the ions. In addition, an analytical model for the electron dynamics is formulated. The formation of the soliton-like structure and the connection between the soliton and the electron dynamics are investigated. The location of the electron group follows a drift equation, while the spatial shape can be described by Poisson-Boltzmann equilibrium in a co-moving frame. A stability analysis is conducted using the Lyapunov method and a linear stability analysis. A comparison of the numerical simulation with the analytical models yields a good agreement.