Electron transfer in proton-hydrogen collisions in nonideal classical plasmas

Effects of nonideality of classical plasma on the reaction: p + H(1s) → H(nlm) + p has been investigated by carrying out fully quantum mechanical calculations within the framework of a first-order distorted wave method. Scattering amplitude is calculated conveniently by employing a simple, variationally determined wave function of hydrogen atom embedded in nonideal classical plasma. A detailed study is made on the changes in electron transfer cross sections due to the nonideality of plasma varying from 0 to 4 and the incident proton energy lying between 10 and 500 keV. It has been found that nonideality of plasma causes substantial change in capture cross section.     

Experimental observation of Coulomb ordered structure in sprays of thermal dusty plasmas

A macroscopic Coulomb-ordered structure of polydisperse CeO₂ particles is observed experimentally in a laminar spray of weakly ionized thermal plasma under atmospheric pressure and temperature of about 1700 K. Diagnostic instruments are used to measure plasma parameters. The particles are charged positively and carry about 10³ electron charges. The calculated values of Coulomb coupling parameter γ_p is > 120, corresponding to a strongly coupled plasma. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 176–180 (10 February 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Electron captures by positrons from hydrogenic ions in nonideal classical plasmas

In nonideal classical plasmas, the electron captures by positrons from hydrogenic ions are investigated. An effective pseudopotential model taking into account the plasma screening effects and collective effects is applied to describe the interaction potential in nonideal plasmas. The classical Bohr-Lindhard model has been applied to obtain the electron capture radius and electron capture probability. The modified hyperbolic trajectory method is applied to the motion of the projectile positron in order to visualize the electron capture probability as a function of the impact parameter, nonideal plasma parameter, projectile velocity, and plasma parameters. The results show that the electron capture probability in nonideal plasmas is always greater than that in ideal plasmas descried by the Debye-Hückel potential, i.e., the collective effect increases the electron capture probability. It is also found that the collective effect is decreased with increasing the projectile velocity. Received 21 January 2000 and Received in final form 27 April 2000     

Diffraction of optical radiation on spatially ordered structures of macroparticles in a strongly nonideal thermal plasma

The first observation of the diffraction of optical radiation on ordered structures of macroparticles in a low-temperature thermal plasma was reported. The experiments were conducted in an air thermal plasma at atmospheric pressure with CeO₂ particles at temperatures 1800–2200 K. The parameters of the plasma medium were determined using probe and optical diagnostics methods. The binary correlation function of the system of macroparticles was reconstructed from measurements of the structure factor. Simulation of nonideal plasma with the parameters corresponding to experiment was performed by the molecular dynamic method. The computed and experimental correlation functions were compared, and it was noted that they are in good agreement with one another.     

Creation of ordered structures in a classical thermal plasma containing macroparticles: Experiment and computer simulation

We have compared experimental measurements of ordered structures in a thermal plasma containing macroparticles of CeO₂ at atmospheric pressure and a temperature around 1700 K with the results of numerical Monte Carlo calculations for the Yukawa model. We describe several distinctive features of the way the experiments were done, including how the ordered macroparticle structures were detected. We discuss a theoretical model of the behavior of an equilibrium system of charged macroparticles in a plasma and the effective interaction potential between them. Good agreement between the experimental and numerical results is noted, and possible reasons for the observed discrepancies are discussed. Zh. éksp. Teor. Fiz. 111, 889–902 (March 1997)     

Kinetics of ionization-recombination processes in nonideal hydrogen plasmas

The time evolution of the relative populations of excited atomic levels in a reacting dense H-plasma is studied on the basis of rate equations. Many-particle effects are taken into account via energy level shifts. It is found that the occupation of the bound state levels is essentially smaller than for the ideal case. It is shown that the mechanism of the relaxation to the thermal equilibrium depends on the density. Inversions of the level populations can be observed.     

Interpolation formula for the electrical conductivity of nonideal plasmas

On the basis of a quantum‐statistical approach to the electrical conductivity of nonideal plasmas we derive analytical results in the classical low‐density regime, in the degenerate Born limit, and for the contribution of the Debye‐Onsager relaxation effect. These explicit results are used to construct an improved interpolation formula of the electrical conductivity valid in a wide range of temperature and density which allows to compare with available experimental data of nonideal plasmas.     

Analysis of mass transfer in dissipative nonideal systems: Experiments on dusty plasmas

Results of an experimental study of mass transfer are presented for extended systems of dust particles observed in capacitively coupled RF discharge plasmas. The Green-Kubo relation and the Langevin equation are validated as applied to dust grain dynamics in laboratory plasmas. A procedure is proposed for evaluating the temperature, friction coefficient, and characteristic oscillation frequency for dust grains. Measured characteristics of the dust subsystem (diffusion coefficient, pair correlation function, and friction coefficient) are compared with available theoretical and numerical results.     

Transformation of the polariton spectrum of nonideal topologically ordered superlattices

The transformation of the polariton spectrum of a nonideal superlattice (a one-dimensional crystal with two elements, layers, in a unit cell) caused by the presence of randomly embedded foreign (with respect to an ideal superlattice) impurity layers is investigated in the framework of the virtual crystal approximation. The obtained specific features of the energy gap as a function of concentration for different values of the polariton branch number testify that the energy structure of the superlattice can be changed significantly by embedding certain impurities into it.     

Equilibrium properties of two-component classical plasmas

Two-component overall neutral classical Coulomb Gas is considered in the canonical ensemble for any value of the space dimensionality ν. The equilibrium properties, i.e. pair correlations and thermodynamic functions are investigated in two complementary ways. The first one is adequate in considering the low temperature range and uses the “molecular” interaction within a pair of unlike charges as a zero order starting point. On the other hand, the high-temperature fully ionized and translation-invariant plasma is considered within the nodal expression with respect to the classical plasma parameter. These two ways are possible through the use of effective temperature-dependent classical interaction for ν > 2. As a by-product, we obtain a unified treatment of the Coulomb Gas thermal properties with respect to dimensionality (integer or real). We also obtain a contrasting comparison with corresponding properties of the one component plasma model which are already known. In this analysis the ν = 2 two-component Coulomb Gas seems to be a landmark for the other TCP'₈. I do not consider degeneracy effects. I consider diffraction corrections in a first order expansion with respect to the Coulomb interaction, in the high-temperature range. The “Hydrogen atom” spectrum is explained for all ν. The long-range hypernetted chain resummation of the pair correlation functions asymptotic behavior does not hold for symmetrical (Z₁ = ?Z₂) plasmas; the corresponding onset of short-range order disappears when the plasma parameter increases. The modified long- and short-range behaviors of the pair correlation functions are then displayed with the canonical thermodynamics.     

Free energy of nonideal two-component thermal plasma

The free energy of nonideal two-component thermal plasma is calculated using the Poisson-Boltzmann equation. The possibility of the existence of a metastable state is shown for a component of heavy multicharged particles with particle charge values bounded from below and plasma temperature values bounded from above. The component of oppositely-charged light singly-charged particles and plasma generally do not feature the metastable state.     

Dynamics of formation of ordered structures in a thermal plasma with macroparticles

The molecular dynamics method is used to model the formation of ordered structures of charged macroparticles in a thermal plasma at atmospheric pressure. The results of the numerical calculations are compared with the experimental data. It is shown that the ordered structure of macroparticles detected experimentally is far from steady state, since the existence time of the plasma in the experiment is less than the characteristic time of formation of the structure. Zh. éksp. Teor. Fiz. 115, 837–845 (March 1999)     

Profile structures of TJ-II stellarator plasmas

Fine structures are found in the TJ-II stellarator electron temperature and density profiles, when they are measured using a high spatial resolution Thomson scattering system. These structures consist of peaks and valleys superimposed to a smooth average. Some irregularities remain in an ensemble average of discharges with similar macroscopic parameters such as line density, central temperature, and plasma current. They are found in all the magnetic configurations explored in plasmas heated by electron cyclotron waves. Their characteristics are shown and their possible origin is discussed.     

Quantum-statistical conductance theory of nonideal plasmas by use of the force-force correlation function method

Using the formalism of force-force correlation functions developed recently, the Spitzer formula for the conductance is generalized by taking into account the following effects: (1) dynamical screening; (2) ion-ion correlations by the ion structure factor; (3) deviations from Coulomb's interaction law; (4) influence of the Debye-Onsager relaxation effect; (5) quantum effects.It is shown that all these effects decrease the conductance in comparison with the values predicted by the Spitzer theory and lead to a more reasonable agreement with the experimental data in the region μ = e²/r_DkT ? 1 (r_D - Debye radius).Electron-electron interactions are treated by a systematic perturbative expansion of the force-force correlation function with the help of the Matsubara Green's function technique.     

Relativistic thermal equilibrium of non-neutral plasmas

Finite temperature effects on the relativistic radial equilibrium of a non-neutral plasma are analyzed. An equation for an effective potential governing the self-consistent radial density profile is derived in the case of global thermal equilibrium. The effect of a finite temperature turns out to be particularly strong for the fast mode of rigid plasma rotation, where the density profile can extend beyond the cold limiting radius.     

Experimental investigation of thermal structures in regular three-dimensional falling films

The European Physical Journal Special Topics - Interfacial waves on the surface of a falling liquid film are known to modify heat and mass transfer. Under non-isothermal conditions, the wave...     

Effect of thermophoretic forces on the formation of ordered structures of macroparticles in a thermal plasma

The thermophoretic interaction of macroparticles and its effect on the formation of ordered structures of macroparticles in plasma was studied. It was shown that coexistence of regions with a chaotic arrangement of particles and regions of ordered structures is typical of a thermal plasma with strong interaction of the macroparticles. Computer simulation of a system of strongly interacting macroparticles, taking account of the thermophoretic interaction of the particles, was performed. The results showed that the thermophoretic attractive forces explain the form of the spatial nonuniformity associated with the grouping of particles in small domains. The experimentally obtained correlation function was very close to the correlation function obtained in the computer simulation. Zh. éksp. Teor. Fiz. 116, 1601–1615 (November 1999)     

初始空间有序分布下超冷等离子体的演化模拟

超冷等离子体是一种极低温的强耦合等离子体.无序诱导加热过程是制约其达到高耦合强度的主要因素.我们使用德拜势场单体系等离子体模型的分子动力学方法模拟超冷等离子体的演化过程,研究初始空间分布对无序诱导加热过程的影响.在周期性边界条件下,我们研究了不同初始空间下超冷等离子体的演化过程,证明了有序初始空间分布能够有效提高等离子体的最终耦合强度,其结果与近期的理论计算相符合.进一步我们在演化模拟中考虑了有限体积下超冷等离子的膨胀过程,发现其在有序初始分布下会引发无序过程显著加热超冷等离子体,导致了耦合强度的逐渐降低.