Correlation effects on the temperature-relaxation rates in dense plasmas

Abstract

We present a model for the rate of temperature relaxation between electrons and ions in plasmas. The model includes self-consistently the effects of particle screening, electron degeneracy and correlations between electrons and ions. We successfully validate the model over a wide range of plasma coupling against molecular-dynamics simulations of classical plasma of like-charged electrons and ions. We present calculations of the relaxation rates in dense hydrogen and show that, while electron-ion correlation effects are indispensable in classical, like-charged plasmas at any density and temperature, quantum diffraction effects prevail over e-i correlation effects in dense hydrogen plasmas.

Molecular dynamics studies of electron-ion temperature equilibration in hydrogen plasmas within the coupled-mode regime

“…Even for H, the demonstration of agreement between MD results and kinetic theory took some time [10][11][12][13], in part because the effect of using the QSPs changes the result slightly even in weak coupling [11]. For the classical like-charge proton-positron system, demonstration of agreement was somewhat more straightforward, motivating a clear connection between the classic LandauSpitzer equilibration rate [15] derived from the Fokker-Planck equation, and a generalized Lenard-Balescu [16] scheme in which both dynamical screening and 2-body static correlations (in the form of local field corrections) are included [8]. Furthermore, it was shown that for many regimes of interest to ICF, the complex dynamical screening of the 2-component (electron + proton) plasma could be replaced by the static response of the electrons alone, yielding identical results [8,9,12,13].…”

“…All but a few of these studies [7,11,14] confined themselves to pure hydrogen (or the proton-positron system [8,9]). Even for H, the demonstration of agreement between MD results and kinetic theory took some time [10][11][12][13], in part because the effect of using the QSPs changes the result slightly even in weak coupling [11].…”

“…Recent work on T -equilibration has involved both kinetic theory of various types [4][5][6][7][8], and MD simulations with like-charges and the pure Coulomb interaction [8,9] as well as opposite-charge simulations with quantum statistical potentials (QSPs) to mock up the effects of quantum diffraction [10][11][12][13][14]. All but a few of these studies [7,11,14] confined themselves to pure hydrogen (or the proton-positron system [8,9]).…”

“…For the classical like-charge proton-positron system, demonstration of agreement was somewhat more straightforward, motivating a clear connection between the classic LandauSpitzer equilibration rate [15] derived from the Fokker-Planck equation, and a generalized Lenard-Balescu [16] scheme in which both dynamical screening and 2-body static correlations (in the form of local field corrections) are included [8]. Furthermore, it was shown that for many regimes of interest to ICF, the complex dynamical screening of the 2-component (electron + proton) plasma could be replaced by the static response of the electrons alone, yielding identical results [8,9,12,13]. This is hardly surprising, since in a given electronproton collision, the "spectator" electrons are expected to move much faster than the much heavier "spectator" protons.…”

“…[20], comparisons were made between the so-called coupled-mode theory (perturbative treatment of Lenard-Balescu including dynamical screening) and the Fermi Golden Rule (FGR) theory [4] (analogous treatment, but where the ion f-sum rule is used to reduce the screening to that of the static response of the electrons [8,20]). The systems considered were hydrogen at a particle density, n = 10 26 cm −3 , and species temperatures:…”