Natalia S. Semeniuk

Theoretical Simulation of a Gas Breakdown Initiated by External Plasma Source in the Gap With Combined Metal–Dielectric Electrodes

This paper is devoted to the theoretical investigation of the breakdown in short discharge gaps of different geometries under the influence of the plasma stream from an external source. The structural feature is the presence of dielectric elements in the electric discharge gap area, which have high emission activity and the ability to accumulate a surface charge. The simulation was performed for a 2-D planar geometry of the discharge gap between two metal electrodes with dielectric coating surrounded by the gaseous medium. Charged particles generation and dynamics have been described by a system of partial differential equations in the diffusion-drift approximation within the two-fluid hydrodynamics plasma model. The basic advantages of the proposed model (such as a wide variety of boundary conditions and geometries of the discharge gap, the scalability of the critical parameters of the environment, and a simple representation of surface reactions) are demonstrated successfully. During computations, the range of gas pressure and the external preionization level at which the probability of low-voltage self-sustained discharge is high enough were identified.

1D simulation of runaway electrons generation in pulsed high-pressure gas discharge

The results of theoretical modelling of runaway electron generation in the high-pressure nanosecond pulsed gas discharge are presented. A novel hybrid model of gas discharge has been successfully built. Hydrodynamic and kinetic approaches are used simultaneously to describe the dynamics of different components of low-temperature discharge plasma. To consider motion of ions and low-energy (plasma) electrons the corresponding equations of continuity with drift-diffusion approximation are used. To describe high-energy (runaway) electrons the Boltzmann kinetic equation is included. As a result of the simulation we obtained spatial and temporal distributions of charged particles and electric field in a pulsed discharge. Furthermore, the energy spectra calculated runaway electrons in different cross-sections, particularly, the discharge gap in the anode plane. It is shown that the average energy of fast electrons (in eV) in the anode plane is usually slightly higher than the instantaneous value of the applied voltage to the gap (in V).

Design and diagnostics of arc-resistant electronics for satellite telecommunication systems

This paper proposes a modern theoretical approach for the complex diagnostics of on-board electronic equipment for the occurrence of primary electric arcing in satellite telecommunication systems. Our method is based on the gradual partitioning of an electronic device into regions that are potentially vulnerable to primary arcing. We solve the complete plasma physics problem with a parametric sweep for each vulnerable region as an independent computational plasma physics problem to obtain the critical parameter diagrams. Each diagram shows the most and least dangerous ranges of critical parameters with respect to the possibility of arcing in a spacecrafts operating conditions. A large set of two-/three-dimensional critical parameter diagrams is widely used for the complex diagnostics and development of electronic systems that are arc-resistance under various operating conditions.

Zero-Dimensional Theoretical Model of Subnanosecond High-Pressure Gas Discharge

This paper deals with the results of the breakdown process simulation in strongly overvoltage gaps under high pressures. The presented 0-D model of discharge enables the estimation of characteristic parameters of the initial stage of the breakdown: current rise rate, time of voltage decay across the gap, and current pulse duration of runaway electrons. The discharge model takes into account 0-D growth kinetics of the plasma density in the gap and the impact of the external power supply circuit of the discharge, including the interelectrode capacitance. The model enables estimation of the number and energy range of runaway electrons generated at the initial stage of high-pressure gas breakdown. As an example, computations were conducted for discharge in nitrogen. A comparison of the simulation results with the experimental data enables estimation of the level of the critical field in which we can expect the generation of runaway electrons in the gas discharge.

Diagnostics of primary arcing in electronics of satellite telecommunication systems

In this paper we propose a modern theoretical approach for complex diagnostics of onboard electronic equipment for the occurrence of primary electric arcing in satellite telecommunication systems. Our method based on the gradual partitioning of the electronic device into regions potentially vulnerable to primary arcing. We solve complete plasma physics problem with parametric sweep for each vulnerable region as an independent computational plasma physics problem in order to obtain the critical parameters diagram. It shows most dangerous and least dangerous ranges of critical parameters with respect to the possibility of arcing in spacecraft operating conditions. A large set of two- and three-dimensional critical parameters diagram is widely used for complex diagnostics and development of arc-resistant electronic systems.

The physical nature of electrons with “anomalous” energies in fast atmospheric discharges

This paper deals with the phenomenon of runaway electrons generation in fast discharges under atmospheric pressures. For the first time we explain the existence of runaway electrons having so-called “anomalous” energies (above the applied voltage value) according to physical kinetics principles. The model we consider provides comprehensive information on the formation and development of runaway electron beams with respect to different initial experimental conditions. The numerical results we obtain fit the existing experimental data for discharges in air.

Modeling of Space Charge Effects in Intense Electron Beams: Kinetic Equation Method Versus PIC Method

In this paper, we present the simulation results for the most important 1-D problems of current flow in planar vacuum diodes. For the first time, classical problems of vacuum electronics have been solved using the basic principles of nonequilibrium physical kinetics. This approach is based on the accurate numerical solution of the Vlasov–Poisson equation system to find the electron distribution function. We have obtained time-dependent numerical solutions that satisfactorily agree with theoretical approximations and with particle-in-cell simulations as well.

Kinetic modelling of the one-dimensional planar virtual cathode oscillator

Our paper presents the simulation results for the one-dimensional virtual cathode oscillator problem solved in terms of computational physical kinetics. Current classical problem of the electron beam injection into vacuum equipotential gap has been solved for the first time using the approach based on accurate numerical solution of Vlasov-Poisson system. We also provide the comparison of obtained results with particle-in-cell simulation and approximate analytical assessments.

Hybrid model of runaway electrons generation process in nanosecond high pressure gas discharge

Summary form only given. The paper deals with the results of theoretical modeling of runaway electrons generation which occurs in the high-pressure nanosecond pulsed gas breakdown. For these purposes a novel hybrid model of the gas discharge has been successfully built. It uses hydrodynamic and kinetic approaches simultaneously to describe the dynamics of different components of low-temperature discharge plasma. Namely, it uses corresponding equations of continuity with drift-diffusion approximation to consider motion of ions and low-energy (Maxwellian) electrons. On the other hand the description of high-energy (runaway) electrons is implemented by including the Boltzmann kinetic equation. Also this system is completed by Maxwell equations set to take into the account the agreed electric field distribution.Numerical solution of equations system allows to describe in details spatial and temporal structure of the plasma, the electric field distribution, as well as the quantity and energy spectrum of runaway electrons that are generated at highvoltage breakdown stage of nanosecond discharge. In contrast to the numerical methods operating with restricted ensemble of particles (i.e. Monte Carlo methods, PIC methods, etc.), the proposed approach allows to calculate the spectrum of a statistically small amount of fast electrons. In particular, it was shown that spectrum of fast electrons at anode depends on the peculiarities of the plasma density and electric field distributions at non-stationary stage of the gas breakdown.

Two-dimensional simulations of gas discharge ignition in short gaps at voltage values below paschen minimum

Summary form only given. In this paper we theoretically investigate the breakdown formation process in discharge gaps where the pd parameter (product of a gap length and a working gas pressure) corresponds to the minimum point neighborhood of the static breakdown voltage curve.Different configurations of metallic electrodes and insulating elements compositions including various forms of dielectric coatings defects are received to study. In simulations the spatial plasma density and corresponding electric field distribution during development of gas discharge after its initiation by an external source of ionizing radiation or a low-temperature plasma flow were calculated in details. As a result of theoretical simulations the range of critical parameters (discharge gap geometry, shapes of electrodes, gas pressures, dielectric constants of the insulation, etc.) has been determined. They are likely to initiate possible breakdown under the influence of an external ionizing source or plasma flows. In particular, it was found that presence of dielectric structures with high emittance leads to significant decrease of the breakdown threshold voltage values that are lower than the Paschens curve minimum.