A technique for plasma velocity-space cross-correlation

TL;DR

This paper introduces a novel experimental technique to measure plasma velocity-space cross-correlation matrices, enabling the detection of collective plasma fluctuations and analysis of eigenmode structures in the ion distribution function.

Contribution

The paper presents the first measurement of a plasma velocity-space cross-correlation matrix using advanced diagnostics and applies singular value decomposition to analyze plasma fluctuation modes.

Findings

First measurement of plasma velocity-space cross-correlation matrix

Identification of plasma fluctuation eigenmodes

Comparison of experimental modes with basic theory

Abstract

An advance in experimental plasma diagnostics is presented and used to make the first measurement of a plasma velocity-space cross-correlation matrix. The velocity space correlation function can detect collective fluctuations of plasmas through a localized measurement. An empirical decomposition, singular value decomposition, is applied to this Hermitian matrix in order to obtain the plasma fluctuation eigenmode structure on the ion distribution function. A basic theory is introduced and compared to the modes obtained by the experiment. A full characterization of these modes is left for future work, but an outline of this endeavor is provided. Finally, the requirements for this experimental technique in other plasma regimes are discussed.