Expansion of a plasma into vacuum with a bi-Maxwellian electron distribution function

A Diaw,P Mora,E Moses,K A Tanaka

doi:10.1051/epjconf/20135917009

Abstract

A comprehensive theory is developped to describe the expansion of a plasma into a vacuum with a two-temperature electron distribution function. The characteristics of the rarefaction shock which occurs in the plasma when the hot- to the cold-electron temperature ratio is larger than 9.9 are investigated with a semi-infinite plasma. Furthermore by using a finite plasma foil, a possible heating of the cold electrons population is evidenced, for a sufficiently large hot- to the cold-electron density ratio.

Highlights

The interaction of lasers with solid targets creates plasmas which may be modeled with a two temperature electron distribution function, as has been observed by experiments [1]
A theory of expansion of a plasma with a bi-Maxwellian electron distribution function is studied both with a fluid and a kinetic model
One distinguishes: the unperturbed plasma, a zone of rarefaction corresponding to the cold electrons expansion, the rarefaction shock, a plateau and a zone of expansion dominated by the hot electrons

Summary

INTRODUCTION

The interaction of lasers with solid targets creates plasmas which may be modeled with a two temperature electron distribution function, as has been observed by experiments [1]. The effects of these two populations of electrons on the expansion of a plasma into a vacuum and on the ion acceleration need to be clarified. In the quasi-neutral and isothermal limits, Bezzerides et al [2] demonstrated that the self-similar model has a multivalued solution when the ratio of the temperature between the hot and the cold electrons is larger than a critical value (≈ 9.9) This breakdown of the self-similar model corresponds to the occurrence of a rarefaction shock wave. With a kinetic model we study the time variation of the cold and hot electrons temperature in the case of a finite plasma foil

THE ELECTRON FLUID MODEL FOR PLASMA EXPANSION

Rarefaction shock

THE ELECTRON KINETIC MODEL FOR PLASMA EXPANSION OF A THIN FOIL

Cold electrons mean temperature

CONCLUSION