Kinetic investigation of the planar Multipole Resonance Probe under arbitrary pressure

TL;DR

This paper develops a collisional kinetic model for the planar Multipole Resonance Probe that applies across arbitrary pressures, enabling improved plasma diagnostics by capturing both collision-less and collisional damping effects.

Contribution

It introduces a new collisional kinetic model for the pMRP that extends previous models to arbitrary pressure conditions, incorporating both kinetic and collisional damping effects.

Findings

The model accurately describes the spectral response of the pMRP.

It enables extraction of electron density, temperature, and collision frequency from measurements.

Both collision-less and collisional damping are observed in the spectral response.

Abstract

Active plasma resonance spectroscopy (APRS) refers to a class of plasma diagnostic methods that use the ability of plasma to resonate at or near the electron plasma frequency for diagnostic purposes. The planar multipole resonance probe (pMRP) is an optimized realization of APRS. It has a non-invasive structure and allows simultaneous measurement of the electron density, electron temperature, and electron-neutral collision frequency. Previous work has investigated the pMRP through the Drude model and collision-less kinetic model. The Drude model misses important kinetic effects such as collision-less kinetic damping. The collision-less kinetic model is able to capture pure kinetic effects. However, it is only applicable to low-pressure plasma. To further study the behavior of the pMRP, we develop a collisional kinetic model in this paper, which applies to arbitrary pressure. In this model, the kinetic equation is coupled to the Poisson equation under the electrostatic approximation. The real part of the general admittance is calculated to describe the spectral response of the probe-plasma system. Both collision-less kinetic damping and collisional damping appear in the spectrum. This model provides a possibility to calculate the electron density, electron temperature, and electron-neutral collision frequency from the measurements.