Anode Plasma Research Articles

Thermal Effect on AMF Electrodes at Different Opening Speeds

The erosion and thermal states at current zero for the axial magnetic field (AMF) electrodes after high-current vacuum arcs (HCVAs) were studied at an average opening speed of 2 m/s. The results obtained are compared with similar results received earlier at an average opening speed of 1 m/s. The discharge was ignited in a demountable vacuum chamber by opening the contacts and was fed with the half-sine current pulse of 10 ms in duration. To determine the thermal state of the surface of the electrodes at zero current, a Phantom MIRO M310 high-speed video camera with a Carl Zeiss 100 mm F2 lens was used. In addition, the surface of the electrodes after the arc exposure was photographed by a Canon camera. The study showed that at the same current an increase of the opening speed leads to an increase in the thermal effect on the electrodes. Besides, the work revealed that at high opening speed (HOS) the process of appearances of erosion traces on the cathodes and, especially, on the anodes, is significantly different. The estimations made in the work showed that the difference in erosion traces on the anode is associated not only with an increase in the thermal effect but also with a change in the momentum transferred to the anode by cathode jets due to jets relaxation in the interaction with the secondary anode plasma in a long arc.

Increasing the Electrical Strength of the Accelerating Gap in an Electron Source with a Plasma Cathode

The stability of operation of an electron source with a plasma cathode with grid (layer) stabilization of the emission-plasma boundary and a plasma anode, whose boundary is open, is investigated. An increase in the stability of the source operation is achieved by reducing the reverse gas and ion flows, when the electron-beam trajectory changes due to the placement of the emission electrode of the electron source and a target in different planes. Calorimetric measurements of the radial distribution of the energy density of the generated electron beam were carried out under the conditions of its deflection and in the “straight” transport mode, when the collector target is on the line of sight relative to the emission electrode. It has been experimentally shown that the stability of the electron-source operation increases by several times when the beam is deflected, thus making it possible to expand the range of the beam parameters and opening up new possibilities for using such an electron source for scientific and technological purposes.

Boundary Conditions in the Source of an Electron Beam on the Surface of the Anode Plasma with a Supersonic Ion Flow

Boundary Conditions in the Source of an Electron Beam on the Surface of the Anode Plasma with a Supersonic Ion Flow

Effect of the residual atmosphere pressure on collective acceleration of ions in the Luce diode

Number and energy of protons and 12C ions collectively accelerated in the Luce diode were determined by radioactivation techniques for residual atmosphere pressure controlled from 5.5 Pa down to 12 mPa. We demonstrate for the first time that the reduction of pressure dramatically reduces average number of 12C ions with energy of up to 2.64eU/amu (U = 250 kV) but in turn increases number of protons accelerated to the same specific energies as well as it enables observation of protons with energies higher than 12eU. We suggest that the 2.64eU/amu protons and 12C ions are accelerated by the same relativistic electron bunches to equal velocities but 12C ions are directly captured in acceleration on the whole way of the bunches from the cathode to the target, while the protons are mostly extracted from the anode plasma.

Increasing Wear Resistance of Alpha- and Beta-Titanium Alloy by Anodic Plasma Electrolytic Boriding

Increasing Wear Resistance of Alpha- and Beta-Titanium Alloy by Anodic Plasma Electrolytic Boriding

Power transferred to the filler wire in twin-body plasma arc welding

In this paper, a heat transfer model of the filler wire in twin-body plasma arc welding (TPAW) was established. The total power transferred to the filler wire included anode effect power, resistance power and plasma arc power. The influences of the wire current, wire extension and plasma gas flow rate on the power transferred to the filler wire were studied using the location of the molten region of the filler wire as the characteristic parameter. The studies showed that the anode effect power caused by the increase in wire current can increase the total power transferred to the filler wire by 50 % or more while the current flowing through the tungsten electrode of the plasma torch remains constant. This is confirmed by analyzing the weld shape under different wire currents. The resistive heating of the wire excision is not a major component of the total power transferred to the filler wire, and the wire extension can be set to a reasonably wide range of values. There was a threshold value for the influence of the plasma gas flow rate on plasma arc power. When the plasma gas flow rate was greater than the threshold value, plasma arc power remained nearly constant as the plasma gas flow rate increased. Therefore, the total power transferred to filler wire in TPAW was composed of anode effect power and plasma arc power.

Токовые характеристики сильноточной электронной пушки с многоканальным инициированием взрывной эмиссии пробоем по поверхности диэлектрика

Current characteristics of a plasma-filled, high-current electron gun with a new cathode assembly which can be named as a controlled explosive-emission cathode have been investigated. Multi-gap initiation of explosive emission is performed with the use of parallel operated, resistively decoupled arc plasma sources which electrodes and tube ceramic isolators are built-in to the explosive-emission cathode. The initiation of explosive emission was performed using 69 operating in parallel arc plasma sources whose electrodes and tubular ceramic insulators are inserted to the disk explosive-emission cathode. Experiments have demonstrated operability of high-current electron gun with a new cathode assembly at accelerating voltage up to 30 kV and its good emissivity (average in area current density) which was approximately 1.4–2.4 times higher than an emissivity of traditional electron gun with plasma anode and multi-wire copper cathode.

The variation in self-organized anode plasma pattern structure with solution electrolyte type in 1 atm DC glow discharge

Plasma self-organization on anode surfaces in 1 atm DC glow discharges remains poorly understood. This effort aims to elucidate the nature of self-organization through the experimental study of resulting patterns on liquid anode surfaces with 13 different electrolytes and thus improves our understanding of the underlying physical processes that give rise to self-organization by investigating electrolyte sensitivity. Self-organization pattern formation and behavior were studied as a function of discharge current, solution ionic strength, and their chemical property evaluation. The response of the patterns to variation in these parameters was measured using an imaging camera and optical emission spectroscopy. Observed pattern characteristic length scales for all of the electrolytes were ranged from 2 to 13 mm and typically increased with current over the investigated range of 20–80 mA. Complex self-organized pattern structures not reported to date were also observed. The parameters associated with pattern formation and morphology complexity are discussed and summarized.

The comparison of cathodic and anodic plasma electrolysis performance in the synthesis of biodiesel

Synthesis of biodiesel using plasma electrolysis is very promising. This study aims to understand the differences between cathodic and anodic plasma performance in synthesizing biodiesel from palm oil. The raw materials used were palm oil, methanol, and KOH catalyst. In the present study, the effects of the type of plasma and the depth of an electrode for biodiesel synthesis were evaluated. The results show that cathodic plasma gave the highest yield of 98.76% and the lowest specific energy consumption of 720 J/ml. Meanwhile, under the same conditions, the anodic plasma gave the highest yield of 96.09% and the lowest specific energy consumption of 910 J/ml. These results indicate that cathodic plasma is better than anodic plasma in synthesizing biodiesel because it gives higher yield and lowers specific energy consumption.

Current state of studies of shock-wave action on the structure and properties of superconductors

The article presents the results of the action of shock waves generated by the Plasma Focus setup on the structure and critical current Jc(B) of MgB2 and Bi-2223-based superconductors. The structure of the tapes was studied in the transverse and longitudinal sections using different impact energy intensities (due to a change in the distance from the plasma anode from 20 to 50 mm for the same number of plasma pulses (n=5)). The studies showed the possibility of increasing the critical current (Jc) up to 50% in transverse and longitudinal magnetic fields to 2-3 T after plasma impact due to changes in the microstructure of the superconducting phase, including: grain refinement, interlayer compaction, microdeformations and crystal lattice defects allowing to increase the number of pinning centers of magnetic vortices.

Mechanism of Processes Stimulated by Ultraviolet Radiation

Modern technologies for creating integrated circuit elements offer many innovations, both in terms of the technological cycle and the introduction of new technologies. Stimulated processes in this regard and their mechanism require a thorough study in order to further improve the technology and the parameters of the micro and nano devices made on their basis. We have studied the processes stimulated by ultraviolet radiation, such as Stimulated Plasma Anodizing and Stimulated Magnetron Sputtering. In the study of stimulated mechanism should be considered processes which are going on with ultraviolet irradiation on the sample and plasma. In these processes, the UV light effects on the plasma, on the surface of the synthesized material, its volume, and the interface area of the material. In particular, in the case of plasma anodizing, UV radiation: 1) produces ozone in the plasma that is much more active than oxygen ion. 2) Ionizes interface area of Plasma-oxide, producing additional current carriers, and 3) transferring electrons from the oxidized material bond zone to the anti-bond zone, thereby weakening the bond strength between the oxide atoms. Because of these effects, the process of mixing anions and cations is facilitated and, consequently, the oxygen diffusion coefficient is increased and the oxidation process is accelerated. At the oxide-semiconductor interface happens roasting existing charge trapping levels, which reduces the concentration of charge carriers and improves the oxide parameters. The same processes are observed in the case of Magnetron Sputtering. In the deposited layer excites mechanical tensions and it can be removed by UV irradiation in the same way as in the case of plasma anodizing.

Specificity of carbon diffusion during plasma electrolytic treatment of steel

This work is devoted to evaluation of the diffusion coefficient of carbon using the thickness of the martensitic layer after plasma electrolytic carburising in various electrolytes followed by quenching. The effective diffusion coefficients of carbon in the structure of mild steel containing oxide and martensitic layers are determined. The maximum diffusion coefficient at a carburising temperature of 900 °C is 23.6. 10−8 cm2/s for treatment in an acetone-based electrolyte for 1 min. The obtained values were comparable with the calculation results for the thickness of the pearlite layer after anodic plasma electrolytic carburising as well as data of measurements of the distribution of carbon concentration in the carburised layer after cathodic saturation. The influence of the oxide layer inhibiting the diffusion of carbon and the possibility of controlling its thickness by varying the concentration of ammonium chloride, which provides anodic dissolution of steel, were confirmed.

Distinctive features of electric current passing through vapour gaseous envelope in anodic plasma electrolytic processes

This article focuses on the study of the effect of anodic composition of electrolyte on electric conductivity of a vapour gaseous envelope, formed in the mode of anode stationary heating. The investigation methods were based on measuring current-voltage characteristics in aqueous solutions of ammonium chloride, chlorohydric acid and hydrobromic acid at equal anion concentrations. It has been established that conductivity in vapour gas medium is primarily determined by electric field intensity which varies depending on its composition and thickness, ion mobility considered as factor of secondary importance. It has been assumed that emissive capacity of aqueous solutions can be limited by a critical concentration of their components.

Increasing wear resistance of austenitic stainless steel by anodic plasma electrolytic nitrocarburising

The effect of plasma electrolytic nitrocarburising on the wear resistance of 12Cr18Ni10Ti steel was investigated. The phase composition of the modified layer and the surface morphology were studied using X-ray analysis and scanning electron microscope. The wear of the specimens was determined with dry friction of the lateral surface of a cylindrical specimen against a bearing steel disc (60 HRC). It is shown that anodic PEN/C of steel samples results in the formation of a hardened layer with a microhardness up to 370 HV due to its saturation with nitrogen and carbon followed by quenching. The wear resistance of steel enhances by 8.5 times after treatment in a solution of carbamide (12 wt. %) and ammonium chloride (10 wt. %) at 800 °C for 5 min with quenching in an electrolyte.

The effect of plasma electrolytic polishing on the surface properties of nitrocarburised steel

The effect of anodic plasma electrolytic polishing on the characteristics of low carbon steel (0.2 % C) after nitrocarburising was investigated. The formation of the modified layer including a hardened diffusion layer and a surface oxide layer occurs as a result of anodic plasma electrolytic nitrocarburising in an aqueous solution of glycerol (8 %), ammonium nitrate (5 %) and ammonium chloride (15 %) at 850 °C. Conducting a plasma electrolytic polishing of the surface leads to the removal of a loose part of the oxide layer (predominantly FeO), which affects the reduction the surface roughness of 2 times. The rate of the weight loss of steel in this process is 0.5 mg/s. The corrosion current density in a 3.5 % sodium chloride solution decreases from 41.0 μA/cm2 in an untreated sample to 32.6 μA/cm2 in the steel after nitrocarburising and polishing during 30 s and to 22–24 μA/cm2 when the second operation lasted 60-300 s due to the protective action of the nitride zone and the dense part of the oxide layer. Wear test shows that plasma electrolytic polishing enhances the wear resistance of a nitrocarburised sample by 1.8 times.

Wear mechanism of medium carbon steel after its plasma electrolytic nitrocarburising

This article considers the change in the tribological characteristics of medium carbon steel after its anodic plasma electrolytic nitrocarburising in a carbamide electrolyte. Phase and elemental composition of the nitrocarburised layer was studied using X-ray analysis and nuclear backscattering of protons. Optical and electron microscopes were used to observe friction tracks. It has been found out that the wear process in nitrocarburised samples is followed by plastic displacement of the metal in the friction contact zone according to the molecular-mechanical and fatigue theory of wear and application of the Kragelsky criterion. It has been shown that an increase in the sliding velocity of 0.5 m/s to 1.5 m/s results in a linear decrease in the friction coefficient from 0.65 to 0.45. The minimum wear rate is achieved after nitrocarburising of steel at 750 °C for 7 min and a sliding speed of (0.4–0.55) m/s. Anodic nitrocarburising increases the wear resistance of steel by 40% compared to quenching at a sliding speed of 0.9 m/s.

Comparison of two types of plasma in contact with water during the formation of molybdenum oxide

The characteristics of an atmospheric pressure glow discharge with a metal cathode and water anode and underwater plasma were compared during the formation of nanostructured molybdenum oxide. The electrical and spectral characteristics of both types of plasma were studied. In both cases, the emission continuum presents in the spectrum because of sputtering the electrode material. The analysis of obtained powder was performed using scanning electron microscopy and x-ray diffraction. Results showed that the mixture of molybdenum oxides is formed for both plasmas.

Anode plasma electrolytic borocarburising of alpha + beta-titanium alloy

The structure of alpha + beta-titanium alloy, its microhardness, surface roughness, and wear and corrosion resistance after anode plasma electrolytic borocarburising (PEB/C) in electrolyte containing boric acid, glycerol and ammonium chloride were investigated. An X-ray diffractometer and scanning electron microscopy were used to characterize the phase composition and structure of the modified surface. Tribological properties of treated titanium alloy were evaluated using a ball-on-disc tribometer under dry testing conditions. The effect of electrolyte compositions on corrosion resistance of the PEB/C samples was examined by means of potentiodynamic polarization in Ringer's solution. It was shown that the electrolyte containing boric acid, glycerol and ammonium chloride provided the saturation of alloy with boron, carbon and oxygen and formation of TiO2 with rutile structure and boron/carbon solid solution in titanium. The anode PEB/C resulted in a decrease in surface roughness by 2.5 times, corrosion current density by 9 times, wear rate by 54 times and an increase in microhardness to 1075 HV10.

Research on 3-GW Repetitively Operating Relativistic Backward Wave Oscillator

Relativistic backward wave oscillator (RBWO) is a promising high-power microwave (HPM) generator. In past decades, many efforts have been devoted to improving its practicality, in which the repetitively operating RBWO has drawn much attention. However, two bottlenecks once limited its development. One is the generation of massive anode plasmas or even damage of the collector, and the other is the RF breakdown of electrodynamic structures. This article describes an RBWO which can operate repetitively with 3-GW microwave power by mitigating these two problems. First, a titanium collector, which shows better performance in resisting electron beam bombardment than the conventional stainless steel collector, is adopted. Meanwhile, water-cooling technology is applied to expedite heat dissipation of the collector. Second, since our investigations demonstrate that an anodic mechanism, not the conventional cathodic mechanism, is the main cause for RF breakdown of electrodynamic structures under strong guiding magnetic field, the titanium material is also used to manufacture the electrodynamic structures of the RBWO in order to increase its power capacity. The advantage of the titanium RBWO is verified in experiments. The application of these techniques, as well as some important surface treatment techniques such as polishing, ultrasonic washing, and vacuum baking, leads to the stable repetitive operation of the RBWO with 3-GW output power and 25-ns microwave duration under a repetition rate of 50 Hz. The successive operation time of the device is up to 20 s.

A study of an external-magnetic insulated ion beam diode with the No. 25 transformer oil anode

An experimental study of a semi-cylindrical external magnetically insulated diode using a polyethylene film and the No. 25 transformer oil acting as anode discharging materials is carried out. The luminescence images of anode plasma and the ion beam current density are acquired using an intensity charge-coupled detector (ICCD) camera and a calibrated Faraday, respectively. The experimental results show that the ion beam current density of the No. 25 transformer oil is higher than that of the polyethylene film. The maximum ion beam current densities at the focus point of the No. 25 transformer oil and the polyethylene film are 325 A/cm2 and 310 A/cm2, respectively. Meanwhile, the lifetime of the No. 25 transformer oil is significantly longer than that of the conventional polyethylene film. The lifetime of the No. 25 transformer oil is about 5000 discharges, while that of the conventional polyethylene film is about 400 discharges. In addition, the ion beam current density of the No. 25 transformer oil is more stable than that of the polyethylene film, and the anode plasma of the No. 25 transformer oil is more uniform than that of the polyethylene film.