I. Ch. Mashek

Effect of gasdynamic processes on structure and threshold of laser spark initiated microwave discharge

The process of the laser-spark-assisted initiation of microwave (MW) discharge in the free space in air has been experimentally studied. It is established that, at a preset MW field intensity, the maximum time for which the laser spark retains its initiating ability increases with the laser pulse energy. In the interval of air pressures of 150–750 Torr, a significant decrease in the MW discharge initiation threshold and the period of retained initiating ability of laser spark are determined by laser-spark-induced gasdynamic perturbations.

Modification of the texture of a polymer material surface in dust plasma

We have analyzed the modification of the texture of polymer particle surface in a dust plasma. Monodisperse spherical melamine formaldehyde particles were injected into the glow discharge plasma in neon. At a certain discharge current and gas pressure in the discharge tube, the particles were suspended in dust-plasma traps and experienced the action of the plasma of 5–25 min. Then, the particles were extracted and the collected material was studied using the scanning electron microscope. Among the results, a change in the diameter and roughness of the surface depending on the residence time of particles in the dust plasma was established. It was found that the absolute deviation of all points of the surface profile averaged over the evaluation length were in the nanometer range. The time of complete degradation of particles in the experimental conditions has been established.

A semiempirical calculation of the fine and Zeeman structure of 4p4f and 4p5f configurations of Ge I. Gyromagnetic ratios

The gyromagnetic ratios (g-factors) belong to the most important characteristics of atoms. For the 4p4f configuration of a germanium atom experimental values of g-factors are available only for four levels, while similar experimental data on the 4p5f configuration of Ge I are absent. Therefore, a theoretical study of the fine and Zeeman structures is topical for determining the gyromagnetic ratios. All the calculations are performed in the one-configuration approximation with the energy-operator matrix containing a maximum possible number of interactions, including magnetic: spin-orbit (own and other), spin-spin, and also orbitorbit interaction. The fine structure has been examined in three (LS, LK, and jK) approximations in order to establish the nature of coupling in the systems studied and the reliability of g-factors. Apart from the g-factors, in studying the Zeeman splitting, its specific features—the crossing and anticrossing fields of magnetic components— have been determined. A comparative analysis of g-factors was performed that showed that our results are in agreement with the available, albeit few in number, experimental data. At all stages, the corresponding energy-operator matrices were numerically diagonalized, i.e., all the results presented in the paper were obtained in the intermediate coupling scheme.

Effect of Mach number on the efficiency of microwave energy deposition in supersonic flow

The article is devoted to experimental and numerical studies of the efficiency of microwave energy deposition into a supersonic flow around the blunt cylinder at different Mach numbers. Identical conditions for energy deposition have been kept in the experiments, thus allowing to evaluate the pure effect of varying Mach number on the pressure drop. Euler equations are solved numerically to model the corresponding unsteady flow compressed gas. The results of numerical simulations are compared to the data obtained from the physical experiments. It is shown that the momentum, which the body receives during interaction of the gas domain modified by microwave discharge with a shock layer before the body, increases almost linearly with rising of Mach number and the efficiency of energy deposition also rises.

Zeeman splitting, its specific features, and gyromagnetic ratios for configurations 1snf (n = 4–10) of the helium atom

The fine structure parameters of configurations 1snf (n = 4–10) with new refined energy values are calculated by the semiempirical method. The emphasis is on the study of the Zeeman structure in order to determine the gyromagnetic ratios of all four the levels of the configuration from the splitting. For this purpose, the matrices of an energy operator with allowance for the interaction between the atom and a magnetic field were diagonalized for all possible values of quantum number M. For each configuration, 17 values of crossing fields of the Zeeman sublevels with ΔМ = ±1, ±2 and the regions of anticrossings with ΔМ = 0 were determined. It is remarkable that, because the levels are closely spaced, anticrossings are observed for each pair of levels in these systems. The regions of linearity of a magnetic field, which are different for different configurations, and the levels in them are established. The g-factors are calculated from the coefficients of an intermediate coupling scheme in a magnetic field that is guaranteed to be linear. They are compared with the analogous values in the absence of a field.

First Breakthrough for Future Air-Breathing Magneto-Plasma Propulsion Systems

A new breakthrough in jet propulsion technology since the invention of the jet engine is achieved. The first critical tests for future air-breathing magneto-plasma propulsion systems have been successfully completed. In this regard, it is also the first time that a pinching dense plasma focus discharge could be ignited at one atmosphere and driven in pulse mode using very fast, nanosecond electrostatic excitations to induce self-organized plasma channels for ignition of the propulsive main discharge. Depending on the capacitor voltage (200-600 V) the energy input at one atmosphere varies from 52-320 J/pulse corresponding to impulse bits from 1.2-8.0 mNs. Such a new pulsed plasma propulsion system driven with one thousand pulses per second would already have thrust-to-area ratios (50-150 kN/m2) of modern jet engines. An array of thrusters could enable future aircrafts and airships to start from ground and reach altitudes up to 50km and beyond. The needed high power could be provided by future compact plasma fusion reactors already in development by aerospace companies. The magneto-plasma compressor itself was originally developed by Russian scientists as plasma fusion device and was later miniaturized for supersonic flow control applications. So the first breakthrough is based on a spin-off plasma fusion technology.

Parameterization of the spectra of configurations 3 p 4 f and 3 p 5 f of a phosphorus ion P II. Gyromagnetic ratios

In the one-configuration approximation, in the formalism of irreducible tensor operators, and in the intermediate (real) coupling scheme, numerical values of the fine-structure parameters are determined for the 3p4f and 3p5f highly excited configurations of the P II phosphorus ion with the energy-operator matrix in the LK-coupling approximation. With these values of the fine-structure parameters, the energy-operator matrix is numerically diagonalized in the LS-coupling approximation. The gyromagnetic ratios calculated in both basis sets in the absence of a field are compared with one another, as well as with their vector counterparts and the experimental g-factors available for the 3p4f configuration. The experimental and theoretical g-factors calculated with the LS basis set are in good agreement with the sole exception of the 3F2 level. Note that the calculation of g-factors from the Zeeman splitting in the linear region totally confirmed their agreement with the values calculated in the LS basis set (gLS) in the absence of a field. The gyromagnetic ratios are the main objectives of this and previous papers, especially for configurations for which experimental data are absent. Apart from the g-factors, the specific features of Zeeman splitting (the crossings and anticrossings of magnetic components) in the 3p5f configurations were determined. These data are to be compared with results of future experiments. Comparison of gyromagnetic ratios calculated in the intermediate coupling scheme with their vector counterparts showed that most levels of the configurations studied are closer than in the LK-coupling scheme.

On the mechanism of own rotation of dust particles

We analyze the physical reason for own rotation of dust particles. We propose from analysis of literature data and our previous studies that own rotation of dust particles is due to azimuth-symmetric flow of ions to the particle surface, which is associated with a nonuniform distribution of the surface charge. This assumption is in conformity with the results of experiments in which the plasma flow is changed by introducing particles in the horizontal plane (horizontal cluster) and particles aligned along the discharge current (vertical cluster) and with the observation of the rotation threshold for the discharge current and the magnetic field. The experiments are performed with spherical particles using the coordinate tracing method. Our results make it possible to construct a model of spinning of charged dust tops for describing magnetic properties of a complex plasma.

Ion drag as a mechanism of plasma dust structure rotation in a strata in a magnetic field

In experiments on complex plasmas, afixed strata region in which the levitation of dust structures is observed is investigated using the method of probing by calibrated dust particles of different sizes in an applied magnetic field under elevated pressures. The measured azimuthal velocity of the probing particles corresponds to the action of the ion drag force for 4 μm-size particles and to the entrainment by the rotating gas owing to the electron vortex flow inside the strata for 1 μm-size particles. Extrapolation to pressures and magnetic fields in which the rotation inversion of dust structures is observed in experiments shows that the ion drag is the dominating force causing rotation with a negative projection of the angular velocity onto the magnetic induction.

Determination of the kinetic coefficients of a gas in a supersonic jet from Brillouin spontaneous scattering spectra

The mean free path and the shear viscosity of molecular nitrogen are determined in a rarefied supersonic jet using the Brillouin spontaneous scattering technique. By examples of sub-and supersonic jets, the measured kinetic coefficients are shown to agree with the tabulated values of these parameters. These results are obtained using laser radiation, whose output power, which restricts the signal-to-noise ratio, is as low as 50 mW.