The spherical multipole resonance probe: kinetic damping in its spectrum

TL;DR

This paper derives an explicit response function for the multipole resonance probe, revealing kinetic damping effects in plasma measurements through a functional analytic approach and spectral analysis.

Contribution

It introduces a novel explicit response function for the multipole resonance probe, highlighting kinetic damping effects in plasma spectroscopy.

Findings

Kinetic effects cause residual damping at zero pressure.

The response function is derived using an algebraic basis expansion.

Spectral analysis reveals additional damping due to kinetic effects.

Abstract

The multipole resonance probe is one of the recently developed measurement devices to measure plasma parameter like electron density and temperature based on the concept of active plasma resonance spectroscopy. The dynamical interaction between the probe and the plasma in electrostatic, kinetic description can be modeled in an abstract notation based on functional analytic methods. These methods provide the opportunity to derive a general solution, which is given as the response function of the probe-plasma system. It is defined by the matrix elements of the resolvent of an appropriate dynamical operator. Based on the general solution a residual damping for vanishing pressure can be predicted and can only be explained by kinetic effects. Within this manuscript an explicit response function of the multipole resonance probe is derived. Therefore, the resolvent is determined by its algebraic representation based on an expansion in orthogonal basis functions. This allows to compute an approximated response function and its corresponding spectra, which show additional damping due to kinetic effects.