Emergence of Kinetic Behavior in Streaming Ultracold Neutral Plasmas

TL;DR

This study demonstrates the emergence of kinetic behavior in streaming ultracold neutral plasmas by controlling electron temperature and density, revealing non-thermal distributions and interpenetrating ion streams through experimental and simulation analysis.

Contribution

It introduces a method to create and analyze streaming ultracold plasmas, highlighting the kinetic phenomena arising from controlled parameters, which was not previously demonstrated.

Findings

Identification of non-thermal ion distributions

Observation of counter-streaming ion populations

Agreement between experimental data and simulations

Abstract

We create streaming ultracold neutral plasmas by tailoring the photoionizing laser beam that creates the plasma. By varying the electron temperature, we control the relative velocity of the streaming populations, and, in conjunction with variation of the plasma density, this controls the ion collisionality of the colliding streams. Laser-induced fluorescence is used to map the spatially resolved density and velocity distribution function for the ions. We identify the lack of local thermal equilibrium and distinct populations of interpenetrating, counter-streaming ions as signatures of kinetic behavior. Experimental data is compared with results from a one-dimensional, two-fluid numerical simulation.