Spatiotemporal evolution of vortex dust structures in a track plasma

Results are presented from experimental studies of the behavior of dust grains in a track plasma produced by an accelerated proton beam. Dynamic dust structures in such a plasma are obtained for the first time, and their spatiotemporal evolution is thoroughly investigated. The structures develop from a dust spiral, which abruptly transforms with increasing dust density into a differentially rotating dust cloud across which dust-sound waves (including spiral waves generated by the dense central core) propagate. As time elapses, the dust cloud loses its fragments and gradually vanishes. At constant experimental conditions, the lifetime of the structures attains a few minutes.     

Self-organization of dust grains in proton beam plasma

The results of investigations of dust grain behavior in plasma formed by a proton beam in inert gases (He, Ar, Kr) are demonstrated. Stable ordered dust structures, namely “a plasma-dust crystal” formed of dust grains 1.0, 3.0, and 4.8 μm in diameter are obtained in the proton beam range for the first time. The mathematical model which allows for numerical simulation of crystal formation from dust grains formed by proton beam plasma is developed.     

Heat transfer in dust structures in an RF discharge plasma

Results are presented from experimental studies of heat transfer in liquid-like plasma-dust structures. The experiments were performed with aluminum oxide grains ～3–5 μm in size in an RF discharge plasma. The heat capacity of the dust grains in plasma is measured. The thermal conductivity and thermal diffusivity of liquid-like plasma-dust structures are deduced under the assumption that the observed temperature gradients and the propagation of a thermal perturbation in a dusty plasma are related to heat conduction within the dust component. The measured temperature dependences of the thermal conductivity and thermal diffusivity are in qualitative agreement with the results of numerical simulations performed in the model of a simple single-atom liquid. It is shown that quantitative discrepancy between the experimental and numerical results is related to the energy loss of dust grains in their collisions with the neutral particles of the ambient gas.     

Dust grain charges in a nuclear-track plasma and the formation of dynamic vortex dust structures

Results are presented from Monte Carlo calculations of the electric charge of dust grains in a plasma produced during the slowing down of the radioactive decay products of californium nuclei in neon. The dust grain charging is explained for the first time as being due to the drift of electrons and ions in an external electric field. It is shown that the charges of the grains depend on their coordinates and strongly fluctuate with time. The time-averaged grain charges agree with the experimental data obtained on ordered liquidlike dust structures in a nuclear-track plasma. The time-averaged dust grain charges are used to carry out computer modeling of the formation of dynamic vortex structures observed in experiments. Evidence is obtained of the fact that the electrostatic forces experienced by the dust grains are potential in character.     

Vortex electron dynamics in a high-current plasma lens

An analytic study is made of the following problems: the instability of a plasma against the excitation of vortex turbulence, the turbulence saturation amplitude, the types and spatial structures of the nascent vortices, and their nonlinear growth rates in an electrostatic plasma lens for focusing high-current ion beams.     

Structures of the plasma channels in a Besselian beam

A mechanism for the formation of the structure of an optical discharge in Besselian laser beams is proposed on the basis of analyzing numerous experiments. The discharge structure is determined by the periodicity of the field of a Besselian beam in the radial and longitudinal directions and also depends on the power and duration of the heating pulse. In the initial stage of the plasma channel formation, the configuration of the channel inhomogeneities follows the discharge structure. If the spatial scale of the discharge structure is small, then the developing channel evolves into a homogeneous state. The time required for the structural inhomogeneities of the plasma channel to be smoothed out is estimated as a function of their scale length. __________ Translated from Fizika Plazmy, Vol. 27, No. 9, 2001, pp. 846–858. Original Russian Text Copyright ￠ 2001 by Pyatnitsky.     

Effect of dust charge fluctuations on dust acoustic structures in magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions

Effect of dust electrical charge fluctuations on the nature of dust acoustic solitary waves (DASWs) in a four-species magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions has been investigated. In this model, the negative dust electric charge is considered to be proportional to the plasma space potential. The nonlinear Zakharov–Kuznetsov (ZK) and modified Zakharov–Kuznetsov (mZK) equations are derived for DASWs by using the standard reductive perturbation method. The combined effects of electron nonextensivity and dust charge fluctuations on the DASW profile are analyzed. The different ranges of the nonextensive q-parameter are considered. The results show that solitary waves the amplitude and width of which depend sensitively on the nonextensive q-parameter can exist. Due to the electron nonextensivity and dust charge fluctuation rate, our dusty plasma model can admit both positive and negative potential solitons. The results show that the amplitude of the soliton increases with increasing electron nonextensivity, but its width decreases. Increasing the electrical charge fluctuations leads to a decrease in both the amplitude and width of DASWs.     

Nonlinear screening of dust grains and structurization of dusty plasma: II. formation and stability of dust structures

The second part of the review on dust structures (the first part was published in Plasma Phys. Rep. 39, 515 (2013)) is devoted to experimental and theoretical studies on the stability of structures and their formation from the initially uniform dusty plasma components. The applicability limits of theoretical results and the role played by nonlinearity in the screening of dust grains are considered. The importance of nonlinearity is demonstrated by using numerous laboratory observations of planar clusters and volumetric dust structures. The simplest compact agglomerates of dust grains in the form of stable planar clusters are discussed. The universal character of instability resulting in the structurization of an initially uniform dusty plasma is shown. The fundamental correlations described in the first part of the review, supplemented with effects of dust inertia and dust friction by the neutral gas, are use to analyze structurization instability. The history of the development of theoretical ideas on the physics of the cluster formation for different types of interaction between dust grains is described.     

Quasilinear relaxation of a low-density electron beam in a plasma

The quasilinear relaxation of a low-density electron beam under the action of plasma turbulence, which is generated during the development of a beam instability, when the beam is formed due to rapid local electron heating (acceleration) is analyzed in the one-dimensional approximation. It is shown that quasilinear diffusion results in the formation of a local plateau at the top of the electron distribution function without causing any significant spread in velocities of the beam electrons and that the relaxation process proceeds primarily through the spatial expansion of electrons with different velocities.     

Chromosome aberration frequencies produced by a 70-MeV proton beam

The effectiveness of a 70-MeV proton beam in the induction of chromosome aberrations was studied. We employed peripheral lymphocytes and analyzed the frequencies of dicentrics and rings after irradiation at doses ranging from 0.1 to 8.0 Gy at various depths within a Lucite phantom. The frequency of chromosome aberrations after irradiation with an unmodulated proton beam at 5 mm showed a dose-response relationship similar to that of 60Co gamma rays. However, irradiation at greater depths with the spread-out Bragg peak induced higher aberration frequencies at doses lower than those with gamma rays. Furthermore, the distribution curve of chromosome aberration frequencies as a function of depth was found to be slightly different from the physically measured depth-dose curve. With the spread-out Bragg peak the biological effects were more marked at greater depths, resulting in a distribution of relative biological effectiveness values. The results obtained from chromosome aberration analysis may not be related directly to those for the relationship between dose and cell killing. Slight differences in values for relative biological effectiveness due to the change of dose and site of proton beam irradiation may not be important for practical proton beam therapy, but may be important in the prevention of late radiation injuries.     

Nonlinear dispersion in a plasma with a relativistic electron beam

The nonlinear interaction of a relativistic electron beam with a plasma is investigated numerically on the basis of the extended notions of the physical quantities that enter the linear dispersion relation. Extending the notions of the wave frequency, wavenumber, and wave phase velocity to the nonlinear stage of an instability makes it possible to analyze the evolution of the Cherenkov and plasma resonances and to study how they affect the saturation of the wave amplitude. A model of the beam-plasma instability in which the growth rate is calculated from the corresponding linear hydrodynamic formula on the basis of the results obtained using a numerical kinetic model makes it possible to establish the applicability range of the hydrodynamic approximation for beams with different energies.     

Electrostatic structures in a plasma and BGK screening

It is shown that the electrostatic attraction between two likely charged plane plates in a plasma can appear due to the formation of “holes” in the phase space of the electrons or ions. The possibility of extending the theory of this effect to the three-dimensional case of a plasma with point dust grains is discussed.     

Mechanism of proton transport by plant plasma membrane proton ATPases

The mechanism of proton translocation by P-type proton ATPases is poorly defined. Asp684 in transmembrane segment M6 of the Arabidopsis thaliana AHA2 plasma membrane P-type proton pump is suggested to act as an essential proton acceptor during proton translocation. Arg655 in transmembrane segment M5 seems to be involved in this proton translocation too, but in contrast to Asp684, is not essential for transport. Asp684 may participate in defining the E₁ proton-binding site, which could possibly exist as a hydronium ion coordination center. A model of proton translocation of AHA2 involving the side chains of amino acids Asp684 and Arg655 is discussed.     

Coherent interaction of a relativistic electron beam with a plasma

Results are presented from experimental studies of the interaction of a modulated relativistic electron beam with a plasma. The electron energy spectra at the exit from the interaction chamber are measured for electron beams with energies of about 50 and 20 MeV. The coherent interaction of an electron beam with a microwave-driven plasma is studied. It is shown that, in strong electric fields that can be generated in the coherent interaction, the beam current is very sensitive to the phase of the microwave field.     

Behavior of a dust grain in the double layer of an electric probe in a gas-discharge plasma

Equations for the motion of an individual dust grain in the double layer of a negatively charged cylindrical probe in a glow discharge plasma are derived and solved numerically. The distribution of the electric potential near the probe is determined, and the grain charge is calculated as a function of the distance from the probe for different probe potentials. The trajectories of grains with different initial energies are traced. An analysis of the grain trajectories shows that, at a certain distance from the probe, high-energy grains may be recharged; i.e., the grain charge may change sign. The grains are found to have no direct effect on the probe current in a dusty plasma of a glow discharge.     

Formation of vortex dust structures in inhomogeneous gas-discharge plasmas

A generalized analytical model of instabilities in a dusty plasma with a nonzero grain charge gradient in a field of nonelectrostatic forces is considered. A review is given of different experimental observations of the dust self-oscillations that occur in the plasmas of an rf capacitive discharge and a dc glow discharge and whose appearance can be explained in terms of the proposed model. It is shown that the change in the grain charge gives rise to dynamic dust structures in laboratory gas-discharge plasmas. Attention is focused on the analysis of the onset of vortex motion of the dust grains.     

Processes accompanying the charging of dust grains in the ionospheric plasma

The influence of the neutral component of the dusty ionospheric plasma on the process of dust grain charging is analyzed. Microscopic ion fluxes onto a dust grain are calculated with allowance for the interaction with the neutral components of the ionospheric plasma for both negatively and positively charged dust grains. For the latter case, which takes place in the presence of intense UV or X-ray solar radiation, the electron heating caused by the photoelectric effect is also investigated. It is found that the efficiency of electron heating depends on the density of neutral particles. The altitudes at which these effects appreciably influence the charging of different types of nano- and microscale dust grains are determined. It is shown that these effects should be taken into account in describing noctilucent clouds, polar mesosphere summer echoes, and physical phenomena involving grains of meteoric origin.     

Nonlinear dynamics of the interaction of a modulated electron beam with a plasma

The excitation of plasma waves during the injection of an unmodulated and a density-modulated electron beam into a semi-infinite cold plasma is investigated. It is shown that the Langmuir oscillation energy accumulated in the plasma increases substantially near the plasma boundary and that the dimension of the region where the Langmuir oscillation energy is localized decreases with time.     

Ion acoustic cnoidal waves in a dusty plasma with a critical dust density

The propagation of nonlinear periodic ion acoustic waves in a dusty plasma is considered for conditions in which the coefficient in the nonlinear equation that describes the quadratic nonlinearity of the medium is zero. An equation that accounts for the cubic nonlinearity of the system is derived, and its solution is found. The dependence of the phase velocity of a cnoidal wave on its amplitude and modulus is determined. In describing the effect of higher order nonlinearities on the properties of a dust ion acoustic wave, two coupled equations for the first- and second-order potentials are obtained. It is shown that the nonlinear ion flux generated by a cnoidal wave propagating in a medium with a cubic nonlinearity is proportional to the fourth power of the wave amplitude.     

Computational modeling of stabilizing the instability of a relativistic electron beam in a dense plasma

The nonlinear dynamics of the instability developed upon the interaction between a relativistic electron beam and a dense plasma as a function of the beam density is numerically modeled. The appropriate solutions are obtained and analyzed.