Microfield distributions in strongly coupled two-component plasmas

The electric microfield distribution at charged particles is studied for two-component electron-ion plasmas using molecular dynamics simulation and theoretical models. The particles are treated within classical statistical mechanics using an electron-ion Coulomb potential regularized at distances less than the de Broglie length to take into account the quantum-diffraction effects. The potential-of-mean-force (PMF) approximation is deduced from a canonical ensemble formulation. The resulting probability density of the electric microfield satisfies exactly the second-moment sum rule without the use of adjustable parameters. The correlation functions between the charged radiator and the plasma ions and electrons are calculated using molecular dynamics simulations and the hypernetted-chain approximation for a two-component plasma. It is shown that the agreement between the theoretical models for the microfield distributions and the simulations is quite good in general.Comment: 18 figures. Submitted to Phys. Rev.

Electrical conductivity of plasmas of DB white dwarf atmospheres

The static electrical conductivity of non-ideal, dense, partially ionized helium plasma was calculated over a wide range of plasma parameters: temperatures $1\cdot 10^{4}\textrm{K} \lesssim T \lesssim 1\cdot 10^{5}\textrm{K}$ and mass density $1 \times 10^{-6} \textrm{g}/\textrm{cm}^{3} \lesssim \rho \lesssim 2 \textrm{g}/\textrm{cm}^{3}$. Calculations of electrical conductivity of plasma for the considered range of plasma parameters are of interest for DB white dwarf atmospheres with effective temperatures $1\cdot 10^{4}\textrm{K} \lesssim T_{eff} \lesssim 3\cdot 10^{4}\textrm{K}$. Electrical conductivity of plasma was calculated by using the modified random phase approximation and semiclassical method, adapted for the case of dense, partially ionized plasma. The results were compared with the unique existing experimental data, including the results related to the region of dense plasmas. In spite of low accuracy of the experimental data, the existing agreement with them indicates that results obtained in this paper are correct

Suprathermal hard X-rays and energetic particles from plasmas "dust"

This work concerns some novel aspects of the simple production of high power density matter in vacuum discharges [1,2] and related energy transport. We study the ensembles of cold grains - hot microplasmas created by an intense energy deposition into the cold solid density, low volume dust "target" collected in the interelectrode space (clusters, grains, microparticles of different size from anode material). Some effects of the high local power density were realised to allow production of the different ensembles of cold grains with fraction of hot microplasmas (T ∼ 1 KeV and ne ∼ 1020-1022 cm -3). The hard x-ray yield registered and well reproduced in the vacuum discharges (just at ∼ 1 J of energy stored) is about 0.1 - 0.3%. Time of flight measurements show that hard x-ray production may be accompanied by energetic ions (∼ 0.1 -1 MeV) like those for irradiated clusters [3]. Thermal and suprathermal levels of x-ray emission, laser-like behaviour of potentially amplifying media of plasmas "dust" as well as x-ray trapping are discussed. The last phenomenon suggests a partial "random walk" of photons inside of x-ray "ball" due to the regulated level of multiple scattering and reflecting in disordered media of cold and hot "grains" of any sizes (x-ray "random" laser [4,5]). Single pass ASE [6] regime of x-ray lasing as particular case of x-ray yield is considered also