Electron Weibel instability induced magnetic fields in optical-field ionized plasmas

TL;DR

This paper reports the first experimental observation of magnetic fields generated by the electron Weibel instability in non-relativistic plasmas created via optical-field ionization, advancing understanding of magnetic field generation in plasmas.

Contribution

It provides the first experimental measurements of Weibel instability-induced magnetic fields in non-relativistic plasmas using optical-field ionization and external electron probes.

Findings

Measured time-resolved magnetic fields in non-relativistic plasmas

Demonstrated controlled initialization of anisotropic electron distributions

Discussed potential extension to quasi-relativistic plasmas

Abstract

Generation and amplification of magnetic fields in plasmas is a long-standing topic that is of great interest to both plasma and space physics. The electron Weibel instability is a well-known mechanism responsible for self-generating magnetic fields in plasmas with temperature anisotropy and has been extensively investigated in both theory and simulations, yet experimental verification of this instability has been challenging. Recently, we demonstrated a new experimental platform that enables the controlled initialization of highly nonthermal and/or anisotropic plasma electron velocity distributions via optical-field ionization. Using an external electron probe bunch from a linear accelerator, the onset, saturation and decay of the self-generated magnetic fields due to electron Weibel instability were measured for the first time to our knowledge. In this paper, we will first present experimental results on time-resolved measurements of the Weibel magnetic fields in non-relativistic plasmas produced by Ti:Sapphire laser pulses (0.8 $\mu m$) and then discuss the feasibility of extending the study to quasi-relativistic regime by using intense $\rm CO_2$ (e.g., 9.2 $\mu m$) lasers to produce much hotter plasmas.