Initializing anisotropic and unstable electron velocity distributions needed for investigating plasma kinetic instabilities

TL;DR

This paper demonstrates that ultrashort laser pulses via optical-field ionization can produce anisotropic, unstable electron velocity distributions in plasma, enabling laboratory study of plasma kinetic instabilities.

Contribution

It introduces a method to generate anisotropic electron velocity distributions using ultrashort laser pulses and verifies their properties with Thomson scattering.

Findings

Produced anisotropic electron distributions using OFI

Observed electron streaming instability within 300 fs

Validated plasma conditions suitable for kinetic instability studies

Abstract

Plasmas with anisotropic electron velocity distribution functions are needed for the controlled study of kinetic plasma instabilities in the laboratory. We demonstrate that such plasma can be produced using ultrashort laser pulses via optical-field ionization (OFI). We experimentally show this control by using Thomson scattering as a diagnostic to probe the characteristic electron velocity distributions using linearly and circularly polarized laser pulses to ionize helium. Furthermore the He plasma produced by a circularly polarized light pulse exhibits the onset of the electron streaming instability within 300 fs of ionization, demonstrating applicability of OFI generated plasmas for studying the kinetic theory regime of plasma physics.