Measurements of the growth and saturation of electron Weibel instability in optical-field ionized plasmas

TL;DR

This study measures the growth and saturation of electron Weibel instability in optical-field ionized plasmas, revealing magnetic field self-organization, agreement with kinetic theory, and magnetic trapping as the saturation mechanism.

Contribution

First experimental measurement of the temporal evolution and saturation of electron Weibel instability in optical-field ionized plasmas.

Findings

Magnetic fields self-organize into a helicoid structure within a few ps.

The growth rate matches kinetic theory predictions including collisions.

Magnetic trapping is identified as the main saturation mechanism.

Abstract

The temporal evolution of the magnetic field associated with electron thermal Weibel instability in optical-field ionized plasmas is measured using ultrashort (1.8 ps), relativistic (45 MeV) electron bunches from a linear accelerator. The self-generated magnetic fields are found to self-organize into a quasi-static structure consistent with a helicoid topology within a few ps and such a structure lasts for tens of ps in underdense plasmas. The measured growth rate agrees well with that predicted by the kinetic theory of plasmas taking into account collisions. Magnetic trapping is identified as the dominant saturation mechanism.