Application of a hybrid model for the numerical study of the generation of runaway electrons and the formation of high-pressure gas discharge

The paper analyses the details of the application of the hybrid model for calculation of the formation of high-pressure gas discharge in conditions where the transition of electrons into runaway mode is possible. In hybrid model, PIC MC method is used only for calculation of runaway electrons, and the standard hydrodynamic approach is used for calculation of plasma electrons. Using such model can significantly reduce computing resources. The results of calculation of kinetics of electrons emitted from a micro-spike on the cathode during the formation of the cathode layer of nanosecond and sub-nanosecond high-pressure gas discharge are presented. The conditions of transition of electrons into runaway mode at this stage and their influence on the further formation of the gas discharge are analyzed. © 2018 Institute of Physics Publishing. All rights reserved.The work was supported by RFBR, Grant 16-08-00894

Atmospheric Pressure Plasma Generation System Based on Pulsed Volume Discharge for the Biological Decontamination of a Surface

The research introduces a system for pulsed volume discharges ignition at atmospheric pressure within gaps reaching 125 mm. The corona discharge is used for the volume discharge initiation. A damping oscillations pulse generator is used as a high-voltage power supply. The pulse repetition rate reaches 1 kHz, while the rate of damping high-frequency harmonic oscillations can reach megahertz units. The volume discharge electric and spectral characteristics were analyzed. The study revealed that O2+ emission spectrum dominates in the UV region. The potential of using pulsed volume discharge for cleaning biological surfaces was demonstrated in the research. The survival rate for E. coli under the influence of 15 seconds long pulsed volume discharge has decreased by 30 times

Research of luminophores afterglow under influence of pulsed X-ray radiation of nanosecond duration

The work describes an investigation of afterglow of various luminophores under influence of pulsed X-ray radiation of nanosecond duration. As a source of radiation a pulsed X-ray "Yasen 01" apparatus is applied. Maximum impulse current of an X-ray tube is 300 A. Maximum electron energy is 120 keV. Half-height pulse duration of an X-ray burst is about 30 ns. A pulse repetition rate is up to 4 kHz. Two types of X-ray luminophores based on gadolinium oxysulfide Gd 2 O 2 S:Tb and cesium iodide CsI:Tl have been investigated. The novelty of the work is use of a fast-acting solid-state semiconductor photomultiplier. It allows recording changes of luminophores luminosity in the nanosecond time range. The photomultiplier is characterized by having two discreet outputs for measuring quickly and slowly time-changing light flows. Presence of two signal outputs allows recording changes of luminophores luminosity both during fast nanosecond excitation and during long-time afterglow. Obtained data about the nature of afterglow of investigated luminophores makes it possible to select the best one for use in conjunction with a pulsed X-ray apparatus with a high pulse repetition rate. © Published under licence by IOP Publishing Ltd

CALCULATION OF THE KINETIC COEFFICIENTS FOR DESCRIPTION OF RUNAWAY ELECTRONS BEAM DYNAMICS

A computer program calculating the kinetic coefficients by the Monte Carlo method for subsequent description of runaway electrons beam dynamics is developed. The calculated coefficients have been compared with corresponding experimental values.Работа поддержана грантом РФФИ №16-08-00894-а

EVALUATION OF INFLUENCE OF THE RUNAWAY ELECTRONS PHENOMENON ON THEIR IONIZATION ABILITY

The previously described algorithm for numerical simulation of electrons motion through a gas-filled accelerating gap has been applied to estimate the effect of the runaway electrons phenomenon on their ionization ability. It has been shown that when the runaway frequency reaches 109 s-1 the electron ionization ability and associated impact ionization coefficient start to decrease. This fact should be taken into account when gas discharge formation process is under consideration.Работа поддержана грантом РФФИ №16-08-00894-а

High-voltage electrode optimization towards uniform surface treatment by a pulsed volume discharge

In this study, the shape and material of the high-voltage electrode of an atmospheric pressure plasma generation system were optimised. The research was performed with the goal of achieving maximum uniformity of plasma treatment of the surface of the low-voltage electrode with a diameter of 100 mm. In order to generate low-temperature plasma with the volume of roughly 1 cubic decimetre, a pulsed volume discharge was used initiated with a corona discharge. The uniformity of the plasma in the region of the low-voltage electrode was assessed using a system for measuring the distribution of discharge current density. The system's low-voltage electrode - collector - was a disc of 100 mm in diameter, the conducting surface of which was divided into 64 radially located segments of equal surface area. The current at each segment was registered by a high-speed measuring system controlled by an ARM™-based 32-bit microcontroller. To facilitate the interpretation of results obtained, a computer program was developed to visualise the results. The program provides a 3D image of the current density distribution on the surface of the low-voltage electrode. Based on the results obtained an optimum shape for a high-voltage electrode was determined. Uniformity of the distribution of discharge current density in relation to distance between electrodes was studied. It was proven that the level of non-uniformity of current density distribution depends on the size of the gap between electrodes. Experiments indicated that it is advantageous to use graphite felt VGN-6 (Russian abbreviation) as the material of the high-voltage electrode's emitting surface

Steerochemistry of heterocycles. - V. Stereochemical peculiarities of 1,3-dioxanes and 1,3-dithianes

The stereochemical peculiarities of substituted 1,3-dioxanes and 1,3-dithianes are discussed. The high probability of the existence of flexible conformations in these series, the considerable energy preference of the 5-C-axial position in the chair conformation of 1,3-dioxanes and 1,3-dithianes, and the definite preference of the 2-C-axial position in the chair conformation of 1,3-dithianes as compared with the axial conformations of the cyclohexane type are noted. The PMR spectra of stereoisomeric 2,5-dimethyl-5-isopropyl-1,3-dioxanes, 2-methy-l5-isopropyl-1,3-dithianes, and 2,2,5-trimethyl-1,3-dithiane are described, and their configurations and preferred conformations are proved. The results of a study of the epimerization of stereoisomers of substituted 1,3-dioxanes and 1,3-dithianes are examined, and the conformational energies of individual substituents in the 5-position of these cyclic systems are calculated on the basis of this examination. © 1973 Consultants Bureau, a division of Plenum Publishing Corporation

4-kW multi-phase battery powered power supply

A method was developed for building the powerful battery power supplies. Using the method, the battery power supply with a 4 kW max power and up to 93% efficiency was developed to supply the "Yasen" X-ray apparatus. Two 60 Acenterdoth series-connected starter lead-acid batteries were used as a primary power supply. A DC output voltage of the source is stable over the entire power range and equals to 310 V. The power supply is based on a 5-phase HF-inverter. There is no difficulty in designing such power supplies with different power outputs. It can be done by the increasing or the decreasing number of phases (of inverter channels). This approach is not limited by the increased number of the inverter channels. The maximum output power will be determined by the battery characteristics only. The power supply is mounted on a mobile trolley, to increase the mobility of the entire set of equipment. The unit dimensions are 410•320•440, the weight is about 40 kg. The unit is forced air-cooled. A power operating mode is short and periodic

New national and regional bryophyte records, 59

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