Using X-ray spectroscopy of relativistic laser plasma interaction to reveal parametric decay instabilities: a modeling tool for astrophysics.

E Oks,T.A Pikuz,I.Yu Skobelev,E Dalimier,A.Ya Faenov,A Andreev,S.A Pikuz,P Mckenna,J Green,N.M.H Butler,M.A Alkhimova,P Angelo,E Tubman,N Woolsey,R.J Dance,N Booth,R Kodama,A Zhidkov,C Gregory

doi:10.1364/oe.25.001958

Abstract

By analyzing profiles of experimental x-ray spectral lines of Si XIV and Al XIII, we found that both Langmuir and ion acoustic waves developed in plasmas produced via irradiation of thin Si foils by relativistic laser pulses (intensities ~1021 W/cm2). We prove that these waves are due to the parametric decay instability (PDI). This is the first time that the PDI-induced ion acoustic turbulence was discovered by the x-ray spectroscopy in laser-produced plasmas. These conclusions are also supported by PIC simulations. Our results can be used for laboratory modeling of physical processes in astrophysical objects and a better understanding of intense laser-plasma interactions.

Highlights

Shapes of x-ray spectral lines emitted by laser-produced plasmas have is a standard tool for measuring the electron density and the temperature of plasmas
In our study the experimental spectral lines were Si XIV and Al XIII lines generated via the interaction of a super-intense laser radiation with thin Si foils
We proved that the ion acoustic turbulence developed at critical density surface of the laserplasma interaction as a result of the parametric decay instability (PDI)

Summary

Introduction

Shapes of x-ray spectral lines emitted by laser-produced plasmas have is a standard tool for measuring the electron density and the temperature of plasmas. Ion acoustic waves (or any other kind of a LET) in laser-produced, high-density plasmas were not discovered experimentally up to now After presenting this discovery, we show that the ratio of the energy density of the turbulent electric fields E2/(8π) to the thermal energy density of the plasma NeT (where T is the plasma temperature)) is of the same order of magnitude as the corresponding ratio in different astrophysical objects: quasars, pulsars, and Seyfert galaxies. These kind of laboratory experiments can serve as a tool to model the PDI in these astrophysical objects. While the dimensional parameters in the two objects differed by many orders of magnitude, the relevant dimensionless parameters were of the same order of magnitude – see, e.g., [30]

X-ray spectra measurements

Brief theory of Langmuir-wave-caused dips in spectral line profiles

Summary