Shock-wave structure in a dispersing plasma

The shock-wave structure in an isotropic plasma is studied in the scale of the Debye shielding radius. The boundary condition at “infinity” is due to the dissipation mechanism of ions reflected from the ion wavefront. The case of the absence of dissipation corresponds to a collisionless shock wave. It is known that there is a critical Mach number above which the laminar shock wave is impossible. In addition, two types of boundary conditions which occur if collisions in an equilibrium high- and low-ionized plasma are taken into account are considered. The reflected ions are assumed to be scattered by electrons in the first case, and the momentum of the reflected ions is assumed to be transferred to uncharged particles in the second case. The critical Mach number of a shock wave does not exist under the conditions of collision dissipation of a flux of reflected ions. St. Petersburg State University, St. Petersburg 198904. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 14–21, May–June, 1998.     

Charge transfer by high-energy electrons onto the leeward surfaces of a solid in a supersonic rarefied plasma flow

Numerical and experimental dependence of equilibrium potentials of the leeward surfaces on the ratio of concentrations of high-energy electrons and positive ions in a supersonic rarefied plasma flow around a solid are obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 13–23, January–February, 2008.     

Effect of negative ions on probe measurements in a chemically reacting plasma at negative probe potentials

Probe measurements in a chemically reacting plasma provide information about certain parameters of the medium, for example, the effective ionization rate [1, 2]. At atmospheric pressure in a low-temperature plasma containing electronegative components with significant electron affinity (of the order of or greater than 1.5 eV) considerable negative ion concentrating may occur. The effect of the negative ions on the volt-ampere characteristic (VAC) of the probe when the chemical reactions in the plasma are assumed to be frozen was investigated in [3, 4]. Here, the VAC is obtained for negative probe potentials with allowance for ionization and electron attachment reactions whose characteristic lengths are of the order of the dimensions of the region disturbed by the probe. Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 163–169, September–October, 1988.     

Measurement of the charge composition of ions in experiments on interaction of a laser plasma flow with a pulsed gas jet

The ion composition of a plasma flow obtained by intense irradiation of a solid target is determined by methods of probing diagnostics and measuring the secondary emission rate. As the ions fly through a dense gas jet, C ⁵⁺ ions are found to recharge to C ⁴⁺ ions and then to C ³⁺ ions. The fraction of high-charge ions in the initial plasma flow and their concentration in the region of interaction with the jet are calculated. The concentration of atoms in the gas jet is estimated on the basis of the integral change in the charge value. Results necessary for analyzing the conditions of experiments on effective charge-transfer pumping and laser generation in the far ultraviolet spectral range are obtained. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 36–43, May–June, 2009.     

Structure of the electrode boundary layers in a gas-discharge plasma

The structure of the electrode zones in a gas-discharge plasma is investigated in the one-dimensional formulation on the basis of asymptotic methods of analysis of the singularly perturbed equations. The causes of the possible appearance of a negative potential jump at the anode and a minimum of the electric field near the cathode are established. A comparison is made with experiment.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.4, pp. 43–51, July–August, 1992.     

Numerical Simulation of Plasma Dynamics in a Nonuniform Magnetic Field

An efficient algorithm is proposed enabling numerical simulations of plasma dynamics in a nonuniform magnetic field. The present numerical data are in good agreement with experimental data obtained in a GOL-3 setup and with previous simulations. The experimentally observed effect of fast transfer of energy to ions is confirmed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 35–45, January–February, 2006.     

Numerical simulation of plasma motion in a magnetic field. Two-dimensional case

A model of dynamics and heating of a plasma cloud in a magnetic field is considered in a two-temperature approximation. Based on a predictor-corrector-type implicit difference scheme, spreading of a plasma cloud in an external magnetic field is numerically simulated, and the influence of this field on spread dynamics is evaluated. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 121–132, May–June, 2007.     

Gas flow activated in an electron-beam plasma

Probe measurements of electron temperature and density, electron energy distribution functions, and plasma potential in a free gas jet activated in an electron-beam plasma and in a planar reactor are presented. The measurements are performed by single, double, and triple electrostatic probes in jets of helium-argon and helium-argon-monosilane gas mixtures. The latter mixture is used to deposit films of microcrystalline and epitaxial silicon. Microcrystalline silicon films of higher quality are obtained in a dense (n_e ≈ 10¹⁷ m⁻³) and cold (T_e ≈ 1.0–0.5 eV) plasma with a low potential (U_sp ≈ 10 V), whereas the growth of monocrystalline silicon films requires a hotter plasma (T_e ≈ 3–5 eV) with a potential U_sp ≈ 15 V. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 3–10, January–February, 2007.     

One method of producing a high-temperature dense plasma

This paper considers the interaction between an absolutely rigid wall or a steel plate and the rarefaction wave arising in solid deuterium when a 30–150 GPa shock wave arrives at the free surface. It is shown that, in the entropy trace near the wall or interface with the plate, a high-temperature plasma arises, in which a thermonuclear fusion is possible, at least, for shock-wave pressures above 70 GPa. The dimension of the plasma region and the time of its establishment are proportional to the distance between the free surface and the wall. Estimates of the proportionality coefficients are given. It is noted that, in this case, unlike in other methods of high-temperature plasma generation, the time of existence of the plasma may not depend on the sound velocity in it. It is shown that, by using a conical solid-state target wit an exit hole, the shock-wave pressure in solid deuterium can be increased from 10 to 100 GPa. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 15–24, May–June, 2009.     

Numerical investigation of the expansion dynamics and generation of magnetic fields in plasma jets

The processes of interaction between concentrated energy fluxes and solid targets have been investigated in a number of studies. The generation of magnetic fields in erosional plasma formations has been experimentally observed [1–4]. However, the evolution of magnetic fields in plasma jets has not yet been studied in sufficient detail. This paper is devoted to a numerical investigation of unsteady three-dimensional erosion plasma flows and the generation in those flows of magnetic fields resulting from the action of laser radiation on solid targets. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 135–140, November–December, 1986. The authors are grateful to I. V. Nemchinov and B. T. Fedyushin for useful discussion of their results.     

Analytic investigation of the anode zone of a higher-pressure glow discharge

The structure of the glow-discharge anode sheath is investigated analytically in the one-dimensional formulation within the framework of a diffusion-drift approximation. Charged particle recombination reduces significantly the anode potential drop and the width of the anode zone. Given fairly heavy current, which is typical of anode spots, the contribution of the diffusion processes becomes significant because of the reduced width of the anode sheath. Analytical estimates of the anode potential drop and the width of the anode sheath which satisfactorily describe the results of numerical calculations are obtained. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 172–180, March–April, 1994.     

Two-fluid magnetohydrodynamic model of plasma flows in a quasi-steady-state accelerator with a longitudinal magnetic field

This paper reports the results of numerical studies of axisymmetric flows in a coaxial plasma accelerator in the presence of a longitudinal magnetic field. The calculations were performed using a two-dimensional two-fluid magnetohydrodynamic model taking into account the Hall effect and the conductivity tensor of the medium. The numerical experiments confirmed the main features of the plasmadynamic processes found previously using analytical and one-fluid models and made it possible to study plasma flows near the electrodes. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 44–55, May–June, 2009.     

Mechanism of formation of cumulative jets in fluid expelled from a plasma accelerator

The results of an experimental investigation into the process of obtaining cumulative water jets from an electrical discharge in a plasma accelerator are presented. The physical mechanism of jet formation in the plasma accelerator and after the emergence of the fluid into the air is discussed. Nikolaev. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 39–44, Septeber–October, 1988.     

Structure of a supersonic erosion plasma jet

A supersonic erosion plasma jet was generated in a heavy-current discharge in a capillary. The jet development diagram is presented. A spectral study of the jet flowing from the capillary is conducted and densitograms of the negatives are presented. The temperatures and electron and ion concentrations are determined. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 181–185, January–February, 1997.     

Influence of the hall effect on plasma compressibility in a strong toroidal magnetic field

The development of the tearing instability is studied in the presence of a high toroidal magnetic field and a high plasma conductivity. The variation of the plasma density is shown to be significant in this case. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 2, pp. 3–9, March–April, 1998.     

Aerodynamic modification of flow over bluff objects by plasma actuation

Particle image velocimetry and smoke visualization are used to study the alteration of the flow field in the wake of a bluff body by use of an alternating current (AC) surface dielectric barrier discharge. Staggered, surface, and buried electrodes were positioned on the downstream side of circular cylinders at conditions of Re _D = 1 × 10⁴−4 × 10⁴ configured to impose a force due to the ion drift that is either along or counter to the free-stream flow direction. Smoke visualization and Particle Image Velocimetry (PIV) in the wake of the flow confirms that the configuration of the surface electrodes and operation of the discharge significantly alters the location of the flow separation point and the time-averaged velocity profiles in the near and distant wake. Measurements of the vibrational and the rotational temperature using optical emission spectroscopy on the N₂ second positive system (C³Π_u–B³Π_g) indicates that the resulting plasma is highly non-equilibrium and discounts the possibility of a thermal effect on the flow separation process. The mechanism responsible for reduction or enhancement of flow separation is attributed to the streamwise force generated by the asymmetric ion wind—the direction of which is established by the electrode geometry and the local surface charge accumulated on AC cycles.     

Forces acting on a coulomb crystal of microparticles in plasma

An equilibrium two-layer structure of charged microparticles in the near-electrode layer of a radio-frequency discharge was simulated numerically using the Monte Carlo method. Depending on gas pressure, the microparticles either move chaotically or form a multilayer structure with a hexagonal lattice in a horizontal plane. Based on the experiment, a mechanism is proposed that describes the unusual structure of a plasma crystal in which particles of the lower layer are located in the vertical direction strictly under the particles of the upper layer and form vertical columns. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 8–15, November–December, 1998.     

Effect of electric field modulation on charge propagation in a low-conducting polar liquid

Unsteady processes of current propagation and formation of charge structures in a low-conducting polar liquid in the electric field of a horizontal capacitor are considered. Free charges are assumed to form in the liquid only owing to unipolar injection from the anode, which arises if the field strength on the anode is greater than a threshold value. The charge distribution in time and space and the evolution of the density of the current through the capacitor and the field strength on the anode are analyzed. It is demonstrated that the time intervals between two charge injections in a variable field (injection periods) may vary depending on the external field period. The density of the current through the capacitor is obtained as a function of the frequency and amplitude of the external field. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 3–12, January–February, 2008.     

Collisional quenching of theA 2∑+(v′=2)HF+ state by He atomsstate by He atoms

Results of an experimental study of the process of quenching of excited states ofHF ⁺ ions in a hydrofluoride-helium electron-beam plasma are reported. The rate constant of quenching ofA ²∑⁺(v′=2)HF⁺ by helium atoms is measured. The ions were excited by activation of the rarefied gas mixture by an electron beam. Diagnostics of internal states of the ions was performed using the electron-vibration-rotation spectrum of their spontaneous emission. Novosibirsk State University, Novosibirsk 630090. Translated from Prikladnay Makhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 16–20, November–December, 1998     

Structure of the internal boundary layer of a gas-discharge plasma in the axisymmetric case

An asymptotic representation for the solution of the problem of the radial structure of the internal boundary (transition) layer and the radial distribution of the basic physical plasma characteristics of the column of a free-burning low-pressure electric are in He is constructed. Sarov. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 185–195, May–June, 1998.