Explore the vast range of titles available.

The work presents the results of an experimental study of the characteristics of the RF capacitive discharge placed in a magnetic field with a predominant radial component. The experiments are performed in the plasma source, which has the geometry of a Hall thruster. The integrated characteristics of the discharge, as well as the axial distribution of the probe ion current in the channel of the plasma source, are measured using three diagrams of the organization of the external discharge circuit: with the open for DC discharge circuit, as well as in the combination of a capacitive discharge with a direct current discharge. The main measurements are made in the argon in the flowrate range of 0.75–1.8 mg/s and the power of the generator 80–300 W at a frequencies of 2, 4, and 13.56 MHz, the induction of the magnetic field lying in the range of 100–300 G. Evaluation of the parameters of the plasma engine based on capacitive RF discharge when working in air, argon and krypton are made.

In plasma physics, mathematical models are very important in determining the discharge behavior. In this research paper, the physical properties of capacitively coupled radio frequency discharges at low pressure are determined by two methods which are Langmuir probe and OPSIAL software using optical emission spectroscopy data. In addition, the mechanical pump is used to form the mechanically forced discharge region, and the forced region is investigated with these methods. Finally, we report the studies on plasma parameters such as electron density and electron temperature. The particle-in-cell method is used for the simulation studies. When OPSIAL calculations and Langmuir data are compared, it is seen that there are some differences between them, but there is a change in the same direction.

The work is devoted to the study of the characteristics of a low-temperature plasma of a high-frequency (HF) discharge ( f = 13 . 56 MHz) ignited between metallic and electrolytic electrodes at atmospheric pressure. Burning of an RF discharge in a diffuse (volumetric) form is observed at the interface between the media between the electrodes. Numerical calculations of the electric field strength and the distribution of the volumetric power density of the Joule heat release before breakdown in a vapor-gas mixture near a metal electrode are presented. The discharge radiation spectrum, plasma composition, and electron density were studied by optical emission spectroscopy. The thermograms of the electrode surface under the conditions of an RF discharge are considered.

Research that both initiated and developed a hybrid IR-laser system based on conversion of Q-switched slab radiofrequency discharge CO and CO2 lasers in various nonlinear crystals is reviewed. The developed broadband laser system operates in the spectral range from ~2 to ~20 μm because of generation of emission at difference and sum frequencies in these crystals.

The development of a thunderstorm cell in the Beijing area according to the results of numerical modeling and field observations is considered. Based on the numerical simulation, it is shown that the most intense electrification process is the separation of charges as a result of collisions of hailstones and cloud crystals. Using the field observations, the relationship between the electrical and radar characteristics of the cloud was investigated. It is demonstrated that the highest positive correlation is observed between the frequency of discharges and the volume of the supercooled part of the cloud above the 0°C isotherm, and the highest negative correlation is revealed between the frequency of discharges and the maximum current in a discharge.

Optically pumped all-rare-gas laser (OPRGL) with unique properties were recently proposed with a possibility to obtain the laser power on the order of hundreds of Watts from a cubic centimeter. To provide high laser efficiency, the pumping radiation has to match the absorption spectrum of the rare gas metastables. To meet this condition a reliable diagnostics of the key parameters of the active medium is required and knowledge of the broadening and shift coefficients for corresponding transitions of rare gases is necessary. In this paper, the diode-laser absorption spectroscopy was employed to determine the pressure shift coefficient for 811.5 nm Ar line. The value of obtained coefficient in pure argon reduced to 300 K is -(2.1 ± 0.1) × 10-10 s-1cm3. In the course of the study the pressure broadening coefficient was also evaluated and found to be (2.4 ± 0.5) × 10-10 s-1cm3.

A pure argon (Ar) plasma formed by a capacitively coupled radio-frequency discharge was analyzed using Doppler-free saturation spectroscopy. The expected line shape was a characteristic of sub-Doppler spectra in the presence of velocity-changing collisions, a narrow Lorentzian centered on a Doppler pedestal, but the observed line shapes contain a multi-peak structure, attributed to opacity of the medium. Laser absorption and inter-modulated fluorescence spectroscopy measurements were made to validate opacity as a driving factor of the observed line shapes. Spectral line shapes are further complicated by the spatial dependence of the pump laser, probe laser and of the absorbing medium, as well as the large absorbance of the transition under investigation. A numerical line shape was derived by accounting for the spatial variation of the pump and probe with a saturated line shape obtained from the rate equations for an equivalent two-level system. This simulated line shape shows good qualitative agreement with the trends observed in the data.

Current concepts of sensory processing in the cerebral cortex emphasize serial extraction and recombination of features in hierarchically structured feed-forward networks in order to capture the relations among the components of perceptual objects. These concepts are implemented in convolutional deep learning networks and have been validated by the astounding similarities between the functional properties of artificial systems and their natural counterparts. However, cortical architectures also display an abundance of recurrent coupling within and between the layers of the processing hierarchy. This massive recurrence gives rise to highly complex dynamics whose putative function is poorly understood. Here a concept is proposed that assigns specific functions to the dynamics of cortical networks and combines, in a unifying approach, the respective advantages of recurrent and feed-forward processing. It is proposed that the priors about regularities of the world are stored in the weight distributions of feed-forward and recurrent connections and that the high-dimensional, dynamic space provided by recurrent interactions is exploited for computations. These comprise the ultrafast matching of sensory evidence with the priors covertly represented in the correlation structure of spontaneous activity and the context-dependent grouping of feature constellations characterizing natural objects. The concept posits that information is encoded not only in the discharge frequency of neurons but also in the precise timing relations among the discharges. Results of experiments designed to test the predictions derived from this concept support the hypothesis that cerebral cortex exploits the high-dimensional recurrent dynamics for computations serving predictive coding.

This paper is concerned with the application of transient complete flux scheme to a radio frequency discharge model in a one-dimensional geometry. The transient complete flux scheme and exponential difference scheme are used to discretize plasma fluxes in space. Temporal discretization is performed by using implicit Euler method and the 2-step backward differentiation formula of first and second orders. Numerical experiments are carried out to evaluate the order and level of accuracy. The results obtained by the complete flux scheme prove to have uniformly second-order accuracy for the spatial error and coincide with solutions calculated from the fourth-order deferred correction technique.

The results of the first experimental series to produce a plasma using the radio frequency discharge (RF) above the ion cyclotron frequency at relatively low magnetic fields (0.5–0.6 T) in the Large Helical Device (LHD) are presented 1.43 MW of RF power produced target plasma with density up to 6 × 1018 m−3 to deuterium. Tangential NBI application into such a plasma increases plasma parameters. Electron temperatures up to ≈0.9 keV and densities up to ≈2.4 × 1019 m−3 had been achieved, and the maximum value of <βdia> was 2.6%. These experiments open possibilities for new regimes of LHD operation which are also interested to W7-X.