Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

TL;DR

This study investigates x-ray polarization in hot plasmas, revealing that higher-order resonant processes significantly influence polarization diagnostics, and emphasizes the necessity of including these processes for accurate plasma analysis.

Contribution

It provides the first comprehensive experimental validation of higher-order resonant contributions to x-ray polarization in hot plasmas, highlighting their importance in diagnostic accuracy.

Findings

Higher-order processes dominate x-ray polarization signals.

Full-order atomic calculations match experimental data.

Neglecting higher-order effects leads to inaccurate plasma diagnostics.

Abstract

We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work.