Volume Streamer Research Articles

SUB-NANOSECOND SWITCHING OF HIGH-VOLTAGE TRIGATRONS

The paper studies the mode of sub-nanosecond switching operation of trigatrons with an operating voltage of up to 1 MV. It is shown that the mode of such activation takes place because of the creation of primary volume streamer in the trigatron discharge gap under the action of a strong non-uniform electric field. The streamer occupies the entire gap and has a weak glow brightness. An estimated analytical calculation of the trigatron switching process in 0.3 ns is given. The process of sub-nanosecond breakdown of a trigatron with an operating voltage of up to 1 MV is presented. During the process the impact ionization after the incoming of a control pulse with a front of no more than 4 ns and an amplitude of 70 kV in the trigatron occurs along the entire length of the discharge gap of down to 12 mm: between the control electrode and opposing main one as well as between the control electrode and the main one covering it. The experimental data on the increase in the brightness of the discharge glow in the trigatron already after the end of the switching process are given. References 12, figures 6.

A computational study of pseudo-filamentary nanosecond pulsed dielectric barrier discharge in atmospheric air

The formation and propagation of pseudo-filamentary dielectric barrier discharge in atmospheric air are investigated through a 2D fluid model. The discharge development can be divided into three stages: the volume streamer stage, the surface streamer stage, and the reverse discharge stage. The simulations show that the streamer head becomes wider and the electron density of the volume streamer head increases six times when the volume streamer interacts with the dielectric, and the volume streamer transforms into the surface streamer after the interaction. Compared with volume streamers, surface streamers have a smaller radius, a higher electric field, and a higher electron density. Furthermore, the parameters that may influence the discharge characteristics are also studied. It is found that a larger dielectric permittivity, a thinner dielectric, or a shorter voltage rise time leads to earlier inception of volume streamers, faster propagation of surface streamers, and higher current density. It is observed that the velocity of the surface streamer increases first, and then, decreases with the accumulated charges on the surface.

Streamer–surface interaction in an atmospheric pressure dielectric barrier discharge in argon

An atmospheric-pressure dielectric barrier discharge (DBD) in argon is investigated using a time-dependent and spatially two-dimensional fluid-Poisson model in axisymmetric geometry. The focus is on the streamer–surface interaction and the cathode-layer formation during the first discharge event in the single-filament DBD driven by sinusoidal voltage. A characteristic structure consisting of a volume streamer propagating just above the dielectric and simultaneous development of an additional surface discharge near the cathode is observed. The analysis of the electric field, electron production and loss rates, and surface charge density distribution shows that the radial deflection of the volume streamer is driven by free electrons remaining in the volume from the Townsend pre-phase and guided by the radial component of the electric field. The surface discharge occurring between the deflected volume streamer, which acts as virtual anode, and the dielectric surface is governed by ion-induced secondary electron emission and the surface charges accumulated on the dielectric.

Генератор плазмы стримерного разряда

A description of the developed nanosecond high-voltage generator of low-temperature plasma based on a volume streamer discharge is given. Plasma is formed in a high-voltage three-electrode gap, one of which is at a floating potential. Plasma is formed when a special switch is triggered, which connects a floating potential electrode, pre-charged with positive streamers, to a grounded electrode. The operation of the generator in a pulse-periodic mode greatly simplifies its application in experimental studies. Its design and electrical circuit are described. The main electrical characteristics and parameters of streamer plasma radiation in the optical and ultraviolet ranges are presented. An example of a specific application of a generator plasma for solving problems of water purification from metal ions (by the example of manganese) using electric discharge technology is given. The use of a low-temperature plasma of a streamer discharge for experimental research in the field of propagation of an ultrahigh-frequency (microwave) signal in an ionized region of the atmosphere (thunderstorm cell) is described.

Numerical simulation of streamer spreading over the water surface

The 2D mathematical model of a streamer in a surface barrier discharge is presented. The discharge was created in nitrogen at atmospheric pressure. The barrier, which can be a dielectric, tap or distilled water, covers a grounded electrode. A pulse voltage of -15 kV with a leading edge of 10 ns is applied to the cathode located above the barrier surface. Calculations of the propagation of a volume streamer from the cathode to the barrier and the surface streamer along the barrier were carried out. The results of calculations show that the discharge current increases at the stage of propagation of a volume streamer and decreases at the stage of propagation of a surface streamer.

Test Results of a Thick Gas Electron Amplifier with a New Design

The results obtained in the study of the avalanche process of electron multiplication in a thick gas amplifier of a new design are presented. The main feature of the device is the separation of the upper and lower parts of the amplifier by a gas gap with the preservation of the polyimide film as an insulator on the inner surface of the hole electrodes. The width of this gap can vary in the range of 0.1–1.0 mm, depending on the electrode size. With this separation, the surface leakage currents are absent between the electrodes and the charge is not induced on the inner surface of the gas-discharge gap. Due to this solution, it is possible to minimize the probability of both surface and volume streamer phenomena that turn into a Geiger or spark discharge. As a result, a pulse amplitude of a few volts was measured across a load of 50 Ω in a gas mixture of Ar + 20% CO2 when the detector was irradiated with a 90Sr β source.

A Repetitive Nanosecond Pulse Source for Generation of Large Volume Streamer Discharge

Using a unipolar pulse with the rise time and the pulse duration in the order of microsecond as the primary pulse, a nanosecond pulse with the repetitive frequency of several kilohertz is generated by a spark gap switch. By varying both the inter-pulse duration and the pulse frequency, the voltage recovery rate of the spark gap switch is investigated at different working conditions such as the gas pressure, the gas composition as well as the bias voltage. The results reveal that either increase in gas pressure or addition of SF6 to the air can increase the voltage recovery rate. The effect of gas composition on the voltage recovery rate is discussed based on the transferring and distribution of the residual space charges. The repetitive nanosecond pulse source is also applied to the generation of large volume, and the discharge currents are measured to investigate the effect of pulse repetition rate on the large volume streamer discharge.

A New Method for the Generation of Large Volume Discharges in Water

The production of large volume streamer discharges is essential to the industrial application of such discharge in water. The use of dielectric-coated electrode was found to have a great influence on the initiation of the streamer discharge as well as the formation of streamer channels. In this paper, a sphere-ring electrode configuration, in which the sphere was coated with a kind of silicon rubber, was put forward to generate multiple radial streamer discharges in tap water by applying a pulse voltage. Different from the previous methods which need very high electric strength and short pulse duration, this kind of electrode configuration can generate large volume streamer discharges in water easily at lower voltage amplitude. The effect of the pulse parameters, such as pulse amplitude and pulsewidth, on the streamer-channel length has been investigated. The influence mechanism of the coated dielectric on the streamer initiation and propagation is discussed in this paper.

Generation of Streamer Discharge Plasma in Water by All Solid-State Pulsed Power

Pulsed power has been used to produce non-thermal plasmas in gases that generate a high electric field at the tip of streamer discharges, where high energy electrons, free radicals, and ozone are produced. Recently, all solid-state pulsed power generators, which are operated with high repetition rate, long lifetime and high reliability, have been developed for industrial applications, such as high repetition rate pulsed gas lasers, high energy density plasma (EUV sources) and water discharges. We have studied and developed repetitive all solid-state pulsed power system for discharge in water. The developed system consists of a photo-voltaic generator, a Pb battery, an inverter, a controller, a command charger, a high-speed thyristor, a magnetic pulse compression circuit and a pulse transformer, and has mobility. This system can generate an output peak voltage of over 100 kV with voltage rise time of 200 ns. In this work, large volume streamer like discharges in water were produced by the developed system and this discharge plasma used to treat algae (Microcystis) with point-to-plane simple electrodes.

Characteristics of Large Volume Discharges in Water using Pulsed Power

One of industrial applications using pulsed power technologies is water treatment by streamer discharges. Streamer discharges in liquid generate high electric fields at the tip of streamers, as well as high-energy electrons, ozone, chemically active species, ultraviolet rays and shock waves. All of these may be utilized to sterilize microorganisms and to decompose molecules and materials. Large volume streamer discharges in water have been produced in order to realize industrial applications. A wire to plane electrode has been used. The influences of applied voltage, electrode separation, electrode geometry on streamer discharges in water are described.

Cleaning of Lakes and Marshes by Pulsed Power Produced Streamer Discharges in Water.

Pulsed power has been used to produce non-thermal plasmas in atmospheric pressure gases that generate a high electric field at the tips of streamer discharges, where high energy electrons, free radicals, ultraviolet rays, and ozone are produced. These manifestations of streamer discharges have been used in the treatment of exhaust gases, removal of volatile and toxic compounds such as dioxin, and the sterilization of microorganisms. Here, large volume streamer discharges in water are described. These streamer discharges in liquids are able to produce a high electric field, high energy electrons, ozone, chemically active species, ultraviolet rays, and shock waves, which readily sterilize microorganisms and decompose molecules and materials. An application of this phenomenon to the cleaning of lakes and marshes is also described.

A hybrid streamer chamber for intermediate energy heavy ions physics

A small volume streamer chamber currently in use at the Lawrence Berkeley Laboratory 88″ cyclotron is described. A series of external solid state telescopes serves both as the event trigger, and to record the energy and particle identification of the leading fragment in the reaction. The application of this device to the study of associated charged particle multiplicities in reactions of 16O+CsI at 16.5 MeV/nucleon is presented to illustrate its capability.