Analysis of Thomson Scattering from Nonequilibrium Plasmas

Abstract

We develop the theory for light scattering as a diagnostic method for plasmas in nonequilibrium states. We show how well-known nonequilibrium features, like beam acoustic modes, arise in the spectra. The analysis of an experiment with strongly driven electrons demonstrates the abilities of the new approach; we find qualitatively different scattering spectra for different times and excellent agreement with the experimental data after time integration. Finally, an analysis of data from dense beryllium suggests that an energetic electron component exists in this experiment as well.

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

“…This effect might be significant at high-fluence irradiation, leading, e.g., to plasma creation. 44,59 However, as we have recently demonstrated in Ref. 42, the effect is small for the lowfluence case leading to the structural transition of diamond, as considered here.…”

“…11,33,35,36,38 A temperature equation is applied to describe low-energy electrons, which reach (nearly) thermal equilibrium already during the first few femtoseconds after the beginning of the laser pulse, following the "bump-on-hot-tail" distribution. 11,33,[44][45][46] The high-energy-electron and the low-energy-electron domains are interconnected, as electrons can gain or lose energy and go from one domain to another. This forms the source/sink terms for the temperature equation, 47,48 as the changing number and energy of low-energy electrons directly affect their temperature.…”

“…Its (partial) thermalization is then known to be very rapid. 11,33,[44][45][46] However, this electron density is only a fraction of a percent of the solid density. It then does not invalidate the applicability of the ground-state-based approach to the band structure of the solid which is presented in the next section.…”

“…This specific value of the cutoff energy has been chosen to include the exponential tail of the low-energy Fermi distribution 11,33,[44][45][46] in the "temperature" domain. In order to prove that our results are independent of a particular choice of E cut , we performed test calculations varying the value of E cut by a few eV around the cutoff value of 10 eV.…”

Nonlinear propagation of coherent electromagnetic waves in a dense magnetized plasma

“…[1][2][3][4][5][6][7][8] It is concerned with the collective behavior of charged particles in dense plasmas in which the electrons are degenerate and the ions non-degenerate. Such dense plasmas are found in astrophysical settings [9][10][11] (e.g., in the cores of white dwarf stars and magnetars) and in warm dense matter, 12 in planetary systems 13 (e.g., in the core of Jupiter), in intense laser-solid compressed density plasma experiments for inertial confined fusion (ICF), 14 and in quantum free-electron-laser (Q-FEL) systems 15,16 for producing coherent x-rays, as well as in metallic thin films/nanostructures 18 and semiconductor devices. 17 In dense quantum plasmas, the degenerate electrons are Fermions and their equilibrium distribution is governed by the Fermi-Dirac statistics.…”