Experimental Realization of an Exact Solution to the Vlasov Equations for an Expanding Plasma

TL;DR

This paper experimentally demonstrates that the expansion of ultracold neutral plasmas follows an exact analytic solution of the Vlasov equations, confirming theoretical predictions for self-similar, adiabatic expansion in a collisionless regime.

Contribution

It provides the first experimental validation of an exact solution to the Vlasov equations for plasma expansion, specifically in the ultracold, collisionless regime.

Findings

Plasma expansion follows the predicted self-similar solution.

Measurements agree with the analytic Vlasov solution.

Expansion dynamics are consistent with adiabatic behavior.

Abstract

We study the expansion of ultracold neutral plasmas in the regime in which inelastic collisions are negligible. The plasma expands due to the thermal pressure of the electrons, and for an initial spherically symmetric Gaussian density profle, the expansion is self-similar. Measurements of the plasma size and ion kinetic energy using fluorescence imaging and spectroscopy show that the expansion follows an analytic solution of the Vlasov equations for an adiabatically expanding plasma.