Auxiliary Discharge Research Articles

Discharge characteristics and parameter diagnosis of brush-shaped air plasma plumes under auxiliary discharge

Atmospheric pressure plasma jet (APPJ) can produce plasma plumes rich in active species, which has a wide scope of applications. From the perspective of applications, it is one of the hot issues in APPJ research to generate a diffuse plasma plume on a large scale. At present, large-scale plasma plume has been produced by noble working gases, which is more economic and valuable if it is reproduced by air used as the working gas. In this work, an APPJ with an auxiliary discharge is proposed, with which a large-scale air plasma plume with a brush shape is produced. Results indicate that the brush-shaped air plume can exist by changing voltage amplitude (<i>V</i><sub>p</sub>) in a certain range. The length and brightness of the plasma plume increase with <i>V</i><sub>p</sub> increasing. The waveforms of voltage and light emission signalindicate that the discharge can start at most once within half a cycle of applied voltage. The probability of discharge and the intensity of light emission pulse for each half a voltage cycle increase with <i>V</i><sub>p</sub> increasing, but the voltage value at the discharge moment decreases with <i>V</i><sub>p</sub> increasing. High-speed imaging study shows that the generation mechanisms of diffuse brush-shaped air plasma plumes and small-scale air plasma are similar, both originating from the temporal superposition of bifurcated normal flow light. In addition, optical emission spectra from the brush-shaped air plasma plume are utilized to study electron temperature, electron density, molecular vibrational temperature, and gas temperature. With <i>V</i><sub>p</sub> increasing, gas temperature is low and almost unchanged, while electron density, electron temperature, and molecular vibrational temperature increase. In addition, OH concentration of the plasma plume is investigated by laser-induced fluorescence, indicating that OH is uniformly distributed, and its concentration increases with the <i>V</i><sub>p</sub> increasing. All these results mentioned above are qualitatively analyzed.

Study of trigger mechanisms of a pseudospark switch configuration with a steady-state auxiliary glow discharge

This paper presents data on investigation of the pseudospark switch whose trigger unit uses a low-current auxiliary glow discharge with hollow cathode and hollow anode. The electrode system of this unit communicates with the main high-voltage gap of the switch due to the aperture in the flat part of one of the trigger electrodes. It is shown that when the electrode with the aperture plays of role of the hollow cathode of the auxiliary discharge, a low parasitic current through the aperture is provided by the ion flow. This ion current does not practically influence on the static breakdown voltage of the main gap. Applying the trigger pulse between the trigger electrodes leads to the pulsed trigger discharge with an enhanced current. At a negative polarity of the trigger pulse, the cavity with aperture turns out into the hollow anode so that the current is able to be intercepted through the aperture to the grounded cavity of the main gap. The plasma is generated in the cavity and the switch is triggered. With the proper selection of the geometry of the trigger electrodes, the delay time to trigger at a level of several tens of nanoseconds is achievable.

Design of Energy-efficient and Energy-efficient Slag Discharge Device for Large-bore Drilling Rigs

Micro pile hole is a kind of bored pile with a diameter of 100~400mm, which has been widely used in the field of transmission line engineering in recent years, and its hole formation usually uses DTH (Down-the-Hole) drilling rig. When DTH drilling rigs operate, the slag discharge method is to use the compressed air provided by the air compressor to blow the muck directly from the bottom of the hole to the ground. However, during the slag discharge process, it is difficult to blow out the muck due to the large cross-sectional area of the annular space between the hole wall and the drill pipe, especially after a certain drilling depth, and it is even more difficult to discharge if wet soil is encountered. Therefore, there is an urgent need to develop a machine for auxiliary slag discharge to improve the efficiency of slag discharge and reduce working energy consumption. In this paper, a barrel slag discharge device connected to the end of the drill pipe and following the drill bit to the bottom of the hole is designed, which can collect and store the rock slag that is difficult to discharge directly outside the hole, achieve a good slag discharge effect, and can reduce the energy consumption of the air compressor and reduce the drilling cost. Through the Fujian UHVDC transmission line project, the reliability and practicability of the barrel slag discharge device are verified.

Optimized algorithm of auxiliary drainage scheme in tailings reservoir rainfall prediction: illustrated with a case study

Under forecasting rainfall condition, rainfall flows into the tailings pond instantaneously, causing water level rising rapidly, thus threatening the safety of the tailings pond. Therefore, it is of great importance to give auxiliary flood discharge measures in emergency situation. This study investigated the optimized calculation algorithm of two combined schemes of lowering the coverplate of tailing ponds and installing additional drainage pumps to determine the recommended scheme of auxiliary drainage measures for tailing ponds under forecast rainfall and proposed the corresponding prediction and calculation method based on the basic data of the water level-reservoir capacity curve of tailing ponds, forecast rainfall parameters, and flood discharge system parameters. The results showed that compared with the precise algorithm, the optimized algorithm does not need to call the main procedure of flood regulation calculation and is of high calculation efficiency and accuracy, calculation time can be controlled within 0.05s. Through the optimized algorithm, the recommended auxiliary drainage scheme for forecast rainfall can be obtained immediately, which can effectively guide tailing pond flood control and drainage activities during the flood season.

Механизм инициирования процесса коммутации короткого вакуумного промежутка вспомогательным искровым разрядом

The results and analysis of experiments are presented, the purpose of which is to study the mechanism of ignition of a high-voltage arc discharge in a vacuum gap. The results indicate that the development of an arc discharge under the presented conditions is occurs mainly due to the ionization of the residual gas by a flow of overheated electrons with an energy of 100−500 eV from an auxiliary spark discharge.

Adaptive Reclosing Scheme Based on Traveling Wave Injection For Multi-Terminal dc Grids

The hybrid dc circuit breaker (HCB) has the advantages of fast action speed and low operating loss, which is an ideal method for fault isolation of multi-terminal dc grids. For multi-terminal dc grids that transmit power through overhead lines, HCBs are required to have reclosing capability due to the high fault probability and the fact that most of the faults are temporary faults. To avoid the secondary fault strike and equipment damage that may be caused by the reclosing of the HCB when the permanent fault occurs, an adaptive reclosing scheme based on traveling wave injection is proposed in this paper. The scheme injects traveling wave signal into the fault dc line through the additionally configured auxiliary discharge branch in the HCB, and then uses the reflection characteristic of the traveling wave signal on the dc line to identify temporary and permanent faults, to be able to realize fast reclosing when the temporary fault occurs and reliably avoid reclosing after the permanent fault occurs. The test results in the simulation model of the four-terminal dc grid show that the proposed adaptive reclosing scheme can quickly and reliably identify temporary and permanent faults, greatly shorten the power outage time of temporary faults. In addition, it has the advantages of easiness to implement, high reliability, robustness to high-resistance fault and no dead zone, etc.

LOW-PRESSURE UNIFORM PLASMA GENERATOR BASED ON HOLLOW CATHODE FOR ION PLASMA TECHNOLOGIES

The current paper describes the results of the improvement of a volumetric high-current low-pressure plasma generator. The device was made on the basis of a hollow cathode with a gas-magnetron ignition of the discharge and an auxiliary arc discharge for the cathode heating up to thermionic emission temperature. The device was operated at a working gas pressure of 0.1...1 Pa and had an electron concentration of 1010…51011 cm-3. It was shown that the addition of the auxiliary electrode after the emission hole of the canoed unit lead to the improvement of generated plasma characteristics. This plasma generator may be used in the processes of ion-plasma technologies (oxidation, nitration in non-hydrogen media), as well as in energy-saving technologies of combined ion-plasma processing of structural materials.

Hollow Cathode Glow Discharge Initiation in a Fore-Vacuum Plasma–Cathode Electron Source

In this article, we present the results of a study on the initiation of a hollow cathode discharge in the electrode system of a fore-vacuum plasma–cathode electron source. It is shown that the development of the hollow cathode effect is facilitated by the back-streaming ion flux of the high-voltage glow discharge (HGD) that arises in the accelerating gap of the electron source. The effect of the type of operating gas and the cathode hollow geometry on the value of the initiating accelerating voltage, which ensures the HGD back-streaming ion flux, have been studied. It is proposed to use an auxiliary pulsed surface flashover discharge to trigger the hollow cathode discharge. The two methods used jointly provide a stable discharge initiation in the entire operating pressure range of the source, including the ultimately low-pressure range where the operation of the hollow cathode discharge in its low-voltage form is still stable.

Influence of Auxiliary Discharge on the Electrophysical Characteristics of Cesium Pulsed Radiation Sources

Influence of Auxiliary Discharge on the Electrophysical Characteristics of Cesium Pulsed Radiation Sources

Numerical modeling of discharge characteristics of a planar magnetron with injection of electrons from auxiliary discharge

We present here a numerical model of a planar magnetron with electron injection from the plasma of an auxiliary discharge with the hollow cathode. The model is based on solving a system of stationary equations using the method of successive approximations. The model takes into account the effects of the current of the injected electrons, the operating gas pressure, the magnetic field induction, the flow of the target material into the plasma, and the change in the plasma mass-to-charge composition due to cathode sputtering by ion bombardment. Typical volt-ampere characteristics of a magnetron discharge with electron injection, as well as the mass-to-charge composition of the created gas-metal plasma, are calculated.

Влияние предыонизации на микроканальную структуру искрового разряда в воздухе в промежутке острие-плоскость

The initial phase of a spark discharge in the gap between the pin (cathode) and a plane 1.5 mm long in atmospheric pressure air under conditions of preliminary photoionization by an auxiliary discharge was investigated by the method of shadow photography. In the absence of preionization, the discharge from the first nanoseconds after breakdown is an aggregate of a large number of micron-diameter channels. It was found that the electron concentration resulting from preionization, estimated at 108  109 cm-3, increases the degree of uniformity of the discharge channel in the near-cathode region; however, in the near-anode region, the channel remains microstructured. Within the framework of the mechanism of microstructure formation due to the instability of the ionization wave front, a criterion for the formation of a uniform discharge is obtained and an explanation of the results obtained is presented.

Investigation of the mechanism of switching a short vacuum gap using an auxiliary spark discharce

The ionization of a rarefied gas in a short gap by a stream of short-wave radiation and fast electrons from the plasma of an auxiliary spark discharge along the dielectric surface is detected, sufficient to initiate an arc discharge in the gap. The density of the ionizing flow of particles and radiation determines the delay time of the switching gap in relation to the start of the auxiliary discharge. With an increase in the initial concentration of free electrons in the main discharge gap, the transition time to an arc discharge is reduced, due to the development of instabilities. Keywords: plasma, arc discharge, spark discharge, ionization, instability.

Influence of preionization on the microchannel structure of a spark discharge in air in a pin-plane gap

The initial phase of a spark discharge in the gap between the pin(cathode) and a plane 1.5 mm long in atmospheric pressure air underconditions of preliminary photoionization by an auxiliary discharge wasinvestigated by the method of shadow photography. In the absence ofpreionization, the discharge from the first nanoseconds after breakdown isan aggregate of a large number of micron-diameter channels. It was foundthat the electron concentration resulting from preionization, estimated at108-109cm-3, increases the degree of uniformity of the discharge channel inthe near-cathode region; however, in the near-anode region, the channelremains microstructured. Within the framework of the mechanism ofmicrostructure formation due to the instability of the ionization wavefront, a criterion for the formation of a uniform discharge is obtained andan explanation of the results obtained is presented. Keywords: spark discharge, preionization, photoionization, instability of the ionization front, microstructure, shadow photography method\

Increasing the energy of the initiating spark discharge in order to reduce and stabilize the delay time in a compact vacuum breaker

The similarity of the switching mechanisms of compact vacuum spark breakers and spark breakers with laser ignition is established at a comparable level of energy flux density in the ignition node–ionization of the residual gas by a stream of short-wave radiation and fast electrons from the cathode spot plasma or laser plasma. This mechanism allows you to effectively reduce the delay in triggering the spark gap by increasing the ignition energy. An experimental study of the advantages of using an ignition circuit with increased energy for controlling small-sized vacuum spark breakers is carried out. There is a steady decrease in the delay time of the spark gap and an increase in the level
 of delay stability. From the point of view of minimization and stability of the delay time of the spark gap, the energy investment in the formation of the initiating plasma occurs most effectively at the spark stage of the auxiliary discharge along the surface of the dielectric in the ignition node.

Increasing the operation stability of the electron accelerator based on ion-electron emission

This paper presents the results of studying the stability of the plasma emitter of an electron accelerator based on ion-electron emission during the transition from self-sustained continuous to self-sustained frequency (up to 50 kHz) repetitively pulsed generation of an auxiliary glow discharge with a hollow cathode with an area of 20.8×103 cm2 The experimental dependences of the probability of the appearance of cathode spots on the walls of a hollow cathode per unit time on the operating modes of the plasma emitter (pressure and type of working gas, amplitude of the auxiliary discharge current) are presented.

Method of nanosecond triggering for a sealed-off pseudospark switch

This paper describes a method of nanosecond triggering for the modified version of the commercially produced pseudospark switch TPI1-10k/50. The switch uses the trigger unit with the auxiliary glow discharge, and the proposed method is based on the principle of the current interception from the trigger unit to the grounded cathode cavity when the trigger pulse arrives. Different electric circuits for triggering have been investigated. In the circuit, where the so-called trigger resistor or the trigger inductance are available, in the whole range of hydrogen operating pressure, the range of the delay time of triggering corresponds to (80–100) ns with a jitter of (3–6) ns. In the electric circuit, where the trigger resistor is shortened, the delay time increases to about (110–140) ns. However, the jitter remains at approximately the same level.

Efficiency of electron beam extraction to the atmosphere in an accelerator based on ion-electron emission

The use of a modern element base makes it possible to create power supplies with a transition from a direct mode of generation of an auxiliary discharge to a pulse-periodic mode with a pulse repetition rate at the level of several tens of kHz. This allows for a more flexible adjustment of the discharge parameters, keeping the average value of its current, but changing its amplitude with a corresponding change in the pulse duty cycle. In this work, using an electron accelerator based on ion-electron emission, generating a wide-aperture electron beam, we research the effect of auxiliary discharge generation mode (direct and pulse-periodic) on the efficiency of electron beam extraction into the ambient atmosphere. It is shown that, in a direct mode of electron beam generation at an accelerating voltage of 150 kV, the beam extraction coefficient does not exceed 0.25. The possibility of increasing the extraction coefficient to K = 0.55 at the same accelerating voltage of 150 kV was demonstrated without making changes to the design of the accelerator, but switching to a pulsed-periodic mode of emission plasma generation.

Minimization of the delay time and its spread in a compact vacuum breaker

The similarity of the switching mechanisms of compact vacuum spark breakers and spark breakers with laser ignition is established at a comparable level of energy flux density in the ignition node–ionization of the residual gas by a stream of short-wave radiation and fast electrons from the cathode spot plasma or laser plasma. This mechanism allows you to effectively 
 reduce the delay in triggering the spark gap by increasing the ignition energy. An experimental study of the advantages of using an ignition circuit with increased energy for controlling 
 small-sized vacuum spark breakers is carried out. There is a steady decrease in the delay time of the spark gap and an increase in the level of delay stability. From the point of view of minimization and stability of the delay time of the spark gap, the energy investment in the formation of the initiating plasma occurs most effectively at the spark stage of the auxiliary discharge along the surface of the dielectric in the ignition node.

Comparison of Auxiliary Diagnostic Methods in Pulmonary Embolism

Aim: We investigated the importance of auxiliary diagnostic methods in cases when computed tomography pulmonary angiography (CTPA) cannot be used in pulmonary embolism (PE) with a high mortality rate.Materials and Methods: Patients were selected after the exclusion criteria were applied in a sample created from a single center. A total of 86 patients included in our study were examined in terms of clinical features, auxiliary diagnostic methods, anticoagulant use, and hospitalization and discharge status according to the massive or segmental involvement of PE in CTPA.Results: The mean age of the patients was 52.29±14.14 years. According to the CTPA results, there were 46 (53.5%) patients with massive involvement and 40 (46.5%) patients with segmental involvement. While there were 38 (82.6%) patients with massive involvement whose right chambers of the heart were dilated in echocardiography (ECHO) results, there were 19 (47.5%) patients with segmental involvement. There was a statistical significance between the massive involvement of CTPA and ECHO result (p=0.001).Conclusion: ECHO may be preferred as an auxiliary radiological method in the diagnosis of PE in emergency departments (ED), especially in massive embolisms.

A Sealed-Off Pseudospark Switch With Nanosecond Stability of Triggering

This article describes the modified version of the commercially produced pseudospark switch TPI1-10k/50 (pulsed current-10 kA and anode voltage-up to 50 kV) and the results of testing. The main idea of the modification was to use the high-voltage electrode system of this switch but to incorporate the novel trigger unit in the main cathode cavity. This unit uses the auxiliary glow discharge with hollow cathode and hollow anode. The modified switch is intentionally developed for parallel operation of a large number of the switches to a common load. In such conditions, the nanosecond triggering stability of the switches is required. The results of tests demonstrate that the minimum delay time of triggering (the time interval between the instant of arrival of the trigger pulse and the instant of starting the main discharge current) amounts to 80 ns with a jitter of 3 ns. At a decreased hydrogen pressure, the delay time is not increased essentially and amounts to 105 ns with a jitter of 6 ns.