Electrical conductivity of a fully ionized plasma at high frequencies

When the frequency of the electric field is of the order of, or larger than, the electron plasma frequency, kinetic equations are no longer valid. The Klimontovich equation linearized in the applied electric field is solved systematically by means of an expansion into powers of the square root of the plasma parameter. A general expression up to second order is obtained for the conductivity σ(ω, k). There exists a large overlap with the results of an earlier paper on the conductivity at low frequencies. This overlap is used to determine a cut-off parameter. The expression for the conductivity serves as a basis for the calculation of the influence of collisions on the dispersion relation for plasma waves. It appears that for small wavenumbers the influence of electron-ion collisions is dominant compared to electron-electron collisions.     

Operatorenmethode zur Lösung der Vlasov-Gleichung mit BGK-Stoßglied und äußerem elektrischem Feld

Irreversible processes in a classical electron plasma are treated on the basis of a linearized Vlasov equation supplemented by Bhatnagar-Gross-Krook terms describing electron-electron and electron-ion collisions correctly. The infinitely extended plasma is under the action of a space- and time-dependent external electric field. A general method of solution with projection operator techniques is given which results in a system of two coupled Volterra integral equations of the convolution type for the internal electric field and the current density. From there follows the electron distribution function, the electric field in the plasma, the electrical conductivity and a very general dispersion relation including Landau and collision damping. The method given can be generalized f. i. for multicomponent plasmas and for strong external electric fields.     

Current-Driven Kink-Like Instability in Collisional Plasmas

The stability of left-hand circularly polarized waves propagating along an external magnetic field with wavelengths much larger than the ion Larmor radius is studied for fully-ionized collisional plasmas carrying a field-aligned current. It is found that, in the presence of electron-ion collisions, this "kink-like" instability has two branches of unstable wavenumbers: a main branch and a resistive branch. The resistive branch owes its existence to electron-ion collisions, but its growth rate is much smaller than that of the main branch, which is typically some fraction of the ion cyclotron frequency. The effect of collisions on the main branch is to reduce its maximum growth rate while extending the range of unstable wavenumbers to larger values. However, these changes are significant only when the electron-ion collision frequency is comparable to the electron cyclotron frequency. The dispersion relation is solved numerically for plasma and magnetic field parameters appropriate to the UCLA arcjet plasma. The results show that, within the framework of an infinite and homogeneous theory, the kink-like instability should occur in this plasma device.     

Three-particle recombination of non-hydrogen-like ions in the presence of plasma microfields

The effect of electric and magnetic plasma microfields on three-particle electron-ion recombination via the highly excited states of a hydrogen-like ion is studied. It is shown that electric microfields impede this process, and at some electron temperature it ceases for sufficiently high plasma density. Magnetic microfields speed up recombination via low-lying states only negligibly. The rate of such recombination into non-hydrogen-like ion states is comparatively higher than for the equivalent hydrogen-like ion states. Zh. éksp. Teor. Fiz. 114, 1230–1241 (October 1998)     

Simulation of plasma flow in toroidal solenoid filters

An improved drift approximation model with an added radial electrostatic field has been successfully developed. Our model provides a computationally efficient way of quantitatively describing the plasma motion and predicting the plasma behavior in the toroidal solenoid in a filtered cathodic vacuum arc (FCVA) system. Storer's (1989) experimental results have been successfully simulated by this model. A good quantitative fit is obtained for our simulation results to the measured ion currents versus distance along the torus for various B field strengths, the attenuation length, and the wall current. The model describes the change of plasma density along the torus and provides the value of the electron-ion collision frequency at various conditions. The effect of the magnetic field and radial electric field on the plasma transportation can be assessed by the simulation and various plasma parameters can be determined. It is found that the radial electric field confines the 3-directional drift of the ions and is one of the most important parameters in determining the ion throughput. For any given B field strength and plasma parameters, there is a peak ion output corresponding to an optimal potential difference which can be obtained by the simulation. Over three times more ion output can be achieved when the torus wall is appropriately biased     

Electrical Conductivity of Nonideal Quasi-Metallic Plasmas

Electrical conductivity formulas are derived from first principles for fully ionized nonideal plasmas. The theory is applicable to an electron-ion system with a 1) Maxwell electron distribution with an arbitrary interaction parameter ? = Ze2n1/3/KT (ratio of the mean coulomb interaction and thermal energies) and 2) Fermi electron distribution with an interaction parameter ? = Ze2n1/3h?2m-1 n2/3 (ratio of the coulomb interaction and Fermi energies). The momentum relaxation time of the electrons in the plasma is calculated based on plane electron wave functions interacting with the continuum oscillations (plasma waves) through a shielded coulomb potential Us(r) = esee exp (-r/?s)/r, which takes into account both electron-ion interactions (s = i) and electron-electron interactions (s = e). It is shown that the resulting conductivity formulas are applicable to higher densities, for which the ideal plasma conductivity theory breaks down because the Debye radius loses its physical meaning as a shielding length and upper impact parameter. The conductivity obtained for classical plasma is of the form ?c = ?c*(KT)3/2/m1/2e2 and agrees with the ideal plasma conductivity formula with respect to the temperature and density dependence for ?/Z ? 0, but its magnitude is significantly reduced as ?/Z increases. For quantum plasmas, the conductivity obtained is of the form ?Q = ?Q*h3n/m2Ze2, which shows that the degenerate plasma behaves like a low-temperature metal.     

Linear response theory for thermoelectric transport coefficients of a partially ionized plasma

Electrical conductivity, thermopower and thermal conductivity for a partially ionized plasma are expressed within an extended Zubarev approach by equilibrium correlation functions. The Green function technique is used to evaluate the correlation functions in different approximations. Improvements of the Lenard-Balescu approximation are considered, which account for dynamical screening effects and higher Born approximations for the electron-electron, electron-ion and electron-atom interaction.     

Numerical Modelling of Impurity Retention in the ITER Tokamak Scrape-off Layer Plasma

The hydrogen plasma and carbon ions flows generated at the target plates in the ITER tokamak scrape-off layer are numerically investigated. A 2D model of hydrogen plasma and impurity ions is presented. The model is based on the electron-ion Braginski fluid equations [1] for hydrogen plasma and rate equations for impurities. Arbitrary level of impurity ions concentration is assumed. Recycling of hydrogen, sputtering and self sputtering of carbon atoms at the target plates are taken into account. Equations of the model are solved in the slab geometry using 2D-multifluid numerical code EPIT [2]. Problems of impurity ions retention and radiation in the divertor volume are analyzed. Results of calculations for ITER tokamak boundary plasma are presented, showing that poor retention is likely at high impurity concentration in the divertor volume. The radiation power can be a significant part of ingoing energy.     

Effect of electron-ion collision on the ion-acoustic solitary wave in a relativistic plasma

Summary We have considered the effect of electron-ion collision on the structure of the solitary wave in a relativistic unmagnetized plasma. In the present analysis we have considered ions to be cold, the electrons hot. The equation obtained for ion velocity is not the usual KdV type but a perturbed version of it, where the perturbing term is proportional to the electron-ion collision frequency. Lastly we have used the method of Bogoliubov-Mitropolsky to study the change in the solitary-wave profile due to this perturbation.     

Improved variational solutions of the Boltzmann–Ziman transport equation. Application to electronic transport in dense plasmas

We study inelastic electron-ion scattering contributions to the thermoelectronic transport coefficients in dense plasmas. They are deduced from improved variational solutions of the Boltzmann–Ziman equation explained in this work. A new expression for the thermopower is proposed which is evaluated in the case of the dense hydrogen plasma.     

Electrical Conductivity of Non-ideal Plasmas and the Ion Distribution Function

The theory of electrical conductivity of electron-ion-systems is developed for a density region which reaches from the region of non-ideal plasmas up to the region of liquid metals. The conductivity is expressed by quantum mechanical correlation functions. Different forms of the electron-ion pseudopotentials are considered. The ion distribution function is derived using the mean spherical approximation (MSA) theory or the nonlinear Debye-theory. Higher order scattering effects are treated by introducing scattering phase shifts for the statically screened electron-ion potential. The numerical results for the conductivity show a SPITZER-like behaviour in the low-density non-degenerate limit where higher order scattering is important, and a ZIMAN-like behaviour in the strongly degenerate high-density limit where the ion distribution functions and the form of the electron-ion pseudopotential become more important.     

Propagation in a warm collisional magnetoplasma enclosed in aconducting cylinder

A study is presented of the propagation of electron plasma waves in a warm collisional plasma filling a conducting cylinder and magnetized strongly in the axial direction, the plasma parameters being taken to be such that the electron-ion collision is the dominant damping process. The attenuation and phase constants are derived in suitably normalized form by using the electrodynamic method. The dispersion and attenuation characteristics for propagation in the lowest order mode in a hydrogen plasma are obtained for various values of the normalized plasma radius αω_pe/c, the electron temperature and electron density being held constant, and the characteristics are compared with those given by the usual quasi-static approximation, which is found to be valid only if αω_pe /c≲1, where α is the plasma radius, ω _pe is the plasma frequency, and c is the velocity of light in free space. The effect of the plasma frequency on the characteristics is investigated     

激光等离子体的单频及双频加热

本文在导出激光等离子体电子、离子耦合方程的基础上求得了单频加热无穷行列特征矩阵的准确解;又求得了在双频加热情况下各种不稳振荡的阈值与增率,并与单频加热作了比较。     

A quantum formulation of the relaxation process and transport coefficients of magnetized plasma

From a quantum collective approach, the momentum relaxation time, through both electron-electron and electron-ion interactions, is obtained based on electron wave functions interacting with the continuum oscillations (plasma waves). The theoretical model presented gives a consistent and complete set of transport coefficients for a dense magnetized plasma. This unified scheme of long- and short-range interactions gives conductivity formulas which are free from the usual Debye length, which loses its physical meaning as an upper impact parameter for relatively high-density, coupled plasma.     

Impact of nonlinear absorption on propagation of microwave in a plasma filled rectangular waveguide

In collisional and ponderomotive predominant regimes, the propagation of microwave in rectangular waveguide filled with collisional plasma is investigated numerically. The dominant mode is excited through an evacuated waveguide and then enters a similar and co-axis waveguide filled with plasma. In collisional predominant regime, the amplitude of electric field is oscillated along propagation path; outset of propagation path due to the electron-ion collision, the intensity oscillations are reduced. Afterward, under competition between the collisional nonlinearity and absorption, the intensity is increased, so the electron density peak is created in middle of waveguide. In ponderomotive predominant regime, the intensity is slowly decreased due to collision, so the electron density is ramped. Control parameters, like the frequency, input power, collision frequency, and background electron density are surveyed that can be used to control propagation characteristics of microwave. This method can be used to control heating of fusion plasma and accelerate charged particle.     

Higher order corrections and temperature effects to ion acoustic shock waves in quantum degenerate electron-ion plasma

The contribution of higher-order nonlinearity and dissipation to nonlinear ion acoustic shock waves (IASWs) is investigated by using the reductive perturbation technique in dense electron-ion plasma. The model consists of degenerate electrons (being either ultrarelativistic or nonrelativistic) and nonrelativistic ion fluid. A nonlinear Burger equation and a linear inhomogeneous Burger-type equation are derived. The inclusion of the higher-order corrections results in creating new shock wave structures, humped IASWs. It is found that the kinematic viscosity and the equilibrium ion number density play important roles in the basic features of the produced IA shocks and the associated electric fields. These findings are devoted to explaining the observed waves propagating in the outer periphery of compact dense stars which mostly consists of hydrogen and degenerate electrons.     

Peculiarities of plasma decay in the afterglow of a low-pressure pulsed discharge in oxygen

Weakly ionized plasma of a pulsed-discharge afterglow in oxygen at low pressures (0.05–0.15 torr) is investigated using probe diagnostics. The plasma conductivity is measured by supplying an additional probing current pulse at a certain instant during the afterglow. The spectral line intensities are also measured to additionally monitor the densities of charged particles. The measurements of the time behavior of the electron density in an oxygen afterglow plasma confirm the previous conclusion that the electrons escape due to enhanced diffusion, which results in the formation of an ion-ion plasma. The possibility of realizing the opposite ultimate case—the detachment decay regime with an increase in the electron density to the density of positive ions in the first stage and the transition to the electron-ion plasma in the second stage—is demonstrated.     

激光等离子体相互作用中的两级质子加速（英文）北大核心CSCD

研究了激光辐射压驱动的两级质子加速的相关问题。当超短超强激光脉冲与处在背景等离子体前方的薄固体平靶相互作用时,在固体靶后部形成一个电子层-离子层组成的双层结构。在激光的不断推进下,双层结构在背景等离子体里以一定速度传播,可以看成运动在背景等离子体中的电场。这样,在背景等离子体中的质子被这个运动电场捕获并能加速到很高的能量。通过二维PIC模拟方法和理论分析研究了质子加速的相关问题。研究结果表明,被加速质子的最大能量达到20GeV。     

Plasma self-oscillations in semiconductors within submillimetre frequency range

In strong electric fields, when the impact ionization becomes intensive and the electron drift velocity may decrease with the growing field, self-oscillating processes arise in semiconductors at very high frequencies up to the submillimetre range. These processes are due to negative dynamic differential conductivity of plasma within the corresponding frequency region. The highest frequency branch results from the excitation of plasma oscillations.     

Unstable twisted modes in interpenetrating space plasmas containing superthermal species

The electrostatic twisted modes with orbital angular momentum and associated kinetic instability are studied in a permeating space plasma containing streaming particle species. The plasma containing superthermal electrons and ions is modeled by using a non-gyrotropic Kappa distribution function which penetrates through a relatively slow moving (static) plasma and gives rise to dispersion, damping and growth of ion-acoustic mode under various conditions. Using the Vlasov-Poisson model, the solutions of twisted modes are defined by Laguerre-Gaussian mode functions, which decompose the plasma distribution function and electric field into components characterized by the axial and azimuthal wave numbers. The dielectric constant is derived and analyzed for threshold condition of wave dispersion and instability in the presence of helical electric field with illustrations. The wave excitations due to penetration of solar wind into cometary clouds or interstellar electron-ion plasmas is examined.