Complex interferometry of magnetized plasma: Accuracy and limitations

Abstract

Expanding laser plasmas, produced by high energy laser radiation, possess both high thermal and magnetic field energy densities. Characterization of such plasma is challenging but may provide essential information needed for understanding its physical behavior. Among the standard experimental techniques used for plasma diagnostics, conventional interferometry is one of the most convenient, informative, and accurate. Attempts to extract more information from each laser shot on large facilities have led to development of complex interferometry, which allows us to reconstruct both plasma electron density and magnetic field distributions from a single data object. However, such a benefit requires more accurate processing, critically important in some situations. This work focuses on quasi-axisymmetric interaction geometry. Starting from basic principles, we present a general analysis, consider main error sources, and obtain plasma density and magnetic field distributions with their derived error bars. A regularization procedure, significantly decreasing an error near the plasma symmetry axis, is proposed and analyzed in detail. With use of synthetic datasets, the presented analysis is generally universal for quasi-axisymmetric plasmas.