Schnell rotierender Lichtbogen als spektroskopische Lichtquelle

An electric arc quickly moved magnetically forms a closed plasma cone or plasma ring between two concentrically arranged electrodes. Aerosols and suspended matters can be brought into the plasma in an optimum manner with a little carrier gas flow, and can be excited to emission. The dates applied and attained till now are: Arc current 5…?20 A, magnetic field strength 10⁴…?4 · 10⁵ A/m, magnetic induction 0.1…?0.3 T, rotation frequency 8…?15 kc, carrier gas air or argon maximum flow 0.5 1/min, intensity increase for CuI-lines up to factor 100. Further applications are possible for special lamps and electric arc diagnostics.     

Air flow control around a cylindrical model induced by a rotating electric arc discharge in an external magnetic field. Part I

The structure and dynamics of a near-wall gas flow produced by a rotating electric arc discharge in an external magnetic field around a cylindrical model without an incoming flow has been investigated. The electric arc on the model has been produced by a combined electric discharge (low-current rf discharge + high-current pulse-periodic discharge). Permanent magnets with induction B ≈ 0.1 T have been placed inside the cylindrical models. Ring electrodes are arranged on the surface of the model. The structure and dynamics of the near-wall gas flow around the cylindrical model have been investigated using high-speed photography, as well as the shadowgraph and particle image velocimetry (PIV) methods.     

Composition and electrocatalytic properties of the coatings formed by the ion-beam-assisted deposition of platinum from a pulsed arc-discharge plasma onto aluminum

The structure, composition, and electrocatalytic properties of the coatings formed on aluminum by ion-beam-assisted deposition of platinum from the plasma of a pulsed arc discharge under conditions where deposited-metal ions are used as deposition-assisting ions are studied. The coating thickness reaches ~30 nm, and the near-surface content of platinum atoms in the coatings is ~2.6 × 10¹⁶ cm^-2. The electrocatalytic activities of aluminum-based electrodes with the coatings in the reactions of electrochemical oxidation of methanol and ethanol, which form the basis for the principle of operation of low-temperature fuel cells (considered as promising chemical sources of an electric current), are significantly higher than the activity of a platinum electrode.     

常压下气体放电等离子体振荡的实验与理论研究

在实验上研究了高压交流电弧发生器电极间隙的气体放电及等离子体振荡, 观察到了气体放电过程中的纳秒脉冲.以电子的流体运动方程和麦克斯韦方程为理论基础, 利用δ函数来描述交变外电场作用下电极处的电子堆积现象,建立了常压下气体放电时等离子体在外电场中振荡的理论模型,通过Laplace变换求解出电极间的放电电压.理论与实验结果基本符合, 从而可估算出实验中等离子体的电子数密度为1.3× 10¹²/m³.     

An Efficient Spectroscopic Control — Technique of the Parameters of Thermic Plasmas Produced under the Condition of a Variable Current

The spectroscopic diagnostics has been carried out as an example for an argon plasma from Maecker-Shumaker type electric arc supplied by periodic variable current. It is shown that the time-dependent runs of intensity of the plasma light may be determined using an ordinary oscilloscope. We have stated that the electron concentration N_e in the plasma is the most sensitive quantity to the current pulsations. In the percentage, N_e variations at the arc axis are approximately the same as the current ones.     

The quark-antiquark pair production mechanism in a quark jet

We assume that $\text{q}\text{q}$ pairs in a quark jet are generated similarly to e⁺e^? pairs in a constant uniform electric field. In this way we obtain relative yields and a lower bound for the average transverse momenta (ATM) of all quark flavors. In particular, the ATM of strange quarks would be larger than those of nonstrange ones. From an analysis of the mass dependence of the widths of the parent-trajectory hadrons an estimation of the radius of the colour electric field tube is obtained.     

Zur Asymmetrie der Reaktion139La(n,α)136Cs mit polarisierten Neutronen

Experimental and theoretical investigations have been performed to determine the thermal conductivity of hydrogen in the temperature range between 2000 and 7000 °K. For this purpose the radial temperature distributions for various currents and theE-I-characteristic of a low current wall-stabilized hydrogen arc have been measured. In the dark region of the arc outside the bright core the temperature and the thermal conductivity between 2000 and 4500 °K were found by means of the schlieren technique. The electron temperature in the core of the arc results from spectroscopic measurements. The gas temperature has been calculated with a formula, derived from the kinetic theory of gases. Assuming a constant collision integralQ _eH ¹¹ the radial distribution of electric conductivity has been calculated according to Langevin's formula. The valueQ _eH ¹¹ =30·10^?16 cm₂ results by comparing the integrated conductance with the measured one. Since now the radial distribution of power input and the temperatures are known, the thermal conductivity between 4500 and 7000 °K can be determined as well. The total course of the heat conductivity shows a strong peak at the temperature of 3740 °K characteristic for the dissociation process.     

Non-stationary conjugate heat exchange and phase transitions at the high-energy surface processing. Part 2. Simulation of the technological processes

The developed general physical-mathematical model, FEM-based calculation procedure as well as the software were in practical use to simulate the processes of the non-stationary conjugate heat exchange and phase transformations during the processing of the surface with a high-concentrated energy fluxes, with a stationary, pulsed, and movable heating sources (the processing, including the surface fusing with a quasilaminar plasma jet, transfer electric arc and impulse electron beam; cleaning of the metal substrate surfaces from an oxide layer with the aid of a cathode vacuum arc, etc). The processes of practical importance with considerably different spatial and temporal scales featuring the density of the heat fluxes power q ∈ [10⁷; 10¹⁴] W/m² have been studied. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 07-08-00209).     

Reactive nitrogen species produced in water by non-equilibrium plasma increase plant growth rate and nutritional yield

Water quality, mineralization, and chemical composition, particularly pH and nitrogen compounds each, play a crucial role in plant development and growth. Treatment of water with non-equilibrium discharges results in the change of its properties and chemical composition, which in turn may affect plant growth process and subsequently agriculture produce quality. Both thermal and non-thermal discharges generated in air or in water produce a number of reactive neutral and charged species, electric fields, and ultraviolet radiation. Plasma treatment of water results in significant change of its properties like pH, oxidation–reduction potential (ORP), conductivity, and concentration of reactive oxygen and reactive nitrogen species (ROS and RNS). Here we report the results of an experimental study of the effect of water treated with different atmospheric plasmas on germination, growth rates, and overall nutritional value of various plants. In the study we have used three types of plasmas: thermal spark discharge, gliding arc discharge, and transferred arc discharge. It is shown that the effects of these plasmas on chemical composition of various types of water are qualitatively different. Non-thermal gliding arc discharge plasma results in lower (acidic) pH, and production of significant amount of oxidizing species (e.g. H₂O₂). Gliding arc discharge also causes significant acidification of water, but it is accompanied by production of reactive nitrogen species (NO, NO₂^? and NO₃^?). Spark discharge treatment results in neutral or higher (basic) pH depending on initial water composition, and production of RNS.     

Spontaneous extinguishing of a vacuum arc in terms of the ectonmodel

Based on the ecton model, a statistical method for studying the processes in the cathode spot of a vacuum arc has been proposed. It has been demonstrated that the spontaneous extinguishing of a DC arc and the effect of “current chopping” inherent in an AC arc are due to the cellular structure of a cathode spot and by the finite lifetime of an ecton. The principal characteristics that are responsible for the stability of the arc operation are the current per cell and the efficiency of the recovery mechanism. The average operative time of the discharge is longer for the materials showing lower currents per cell. The influence of the conditions of arc operation, such as the parameters of the external electric circuit, the cathode surface condition, the presence (or absence) of an external electric field, etc., is reduced in the main to a change in the efficiency of the recovery mechanism     

Interaction of Pd cluster anions (Pdn -, n < 11) with oxygen

Interactions between oxygen and Pd cluster anions were studied using Time-of-Flight (ToF) mass spectrometry and Ultraviolet Photoelectron Spectroscopy (UPS). In contrast to the coinage metal clusters, no pronounced size selectivity towards chemisorption of oxygen molecules can be observed for the Pd cluster anions: regardless of the cluster size, no more than 2 oxygen molecules can be attached to a cluster. When Pd_nO_m ^- clusters are prepared by pre-dissociation of oxygen molecules by electric arc and post-reaction with Pd, the proportion of Pd cluster anions reacted with oxygen does not much change compared to the case of the reaction between Pd cluster anions and O₂ molecules. This result indicates that the O₂ chemisorption on Pd cluster anions does not involve large activations barriers: using different synthesis method of a cluster, one can get a better insight into the chemisorption routes of molecules on metal clusters.     

Drift theory of charged-particle motion for a strong electric field in a weakly relativistic approximation

Drift equations of motion are derived for a charged particle in the case of a strong electric field with allowance for relativistic effects of order v²/c². The role of these effects is discussed along with the effects of a high-frequency field. The cases of weak and strong electric fields are distinguished [2] in the drift theory of the motion of charged particles in weakly inhomogeneous magnetic and electric fields. In the case of a weak electric field, the electric-drift velocity is v_E v, where v is the characteristic velocity of the particle. For a strong electric field,v _Ev.The drift theory has now been reasonably well developed for the case of weak electric fields in the classical and relativistic cases, for the absence of high-frequency fields and for the presence of these [1–3], Extension of the theory to strong electric fields involves considerable mathematical difficulties, and this has been done only in the classical approximation with and without hf fields [2–4], Here we consider the drift theory of charged-particle motion for the case of a strong electric field in the weakly relativistic approximation, incorporating terms of order v²/c², where c is the velocity of light. Also hf fields may be present.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 7–9, September, 1981.     

Positioning of the arc discharge channel in vacuum arc facilities

The behavior of an electric arc in a magnetic field is studied theoretically and experimentally. It is found that the arc behavior can be governed by the ponderomotive interaction of the arc with current-carrying elements. In a nonuniform magnetic field, the behavior of the arc depends on the Hall currents and the diamagnetic properties of its plasma. It is shown that the position of the arc channel between the end faces of cylindrical electrodes can be controlled by nonuniform magnetic fields. The methods and devices considered in this paper allow one, in particular, to control arc heat sources used in the heat treatment of metals.     

真空绝缘堆均压环的结构优化

采用数值模拟法和有限元网格细化法对比给出电场的合理参考范围,分别选取距离阴极三结合点(0.005)(21/2d)处(d是绝缘体的厚度)和距离阳极三结合点(0.008 5)(21/2d)处的电场强度为参考点。通过优化均压环形状,采用阴极激发闪络和阳极激发闪络两种模型来控制三结合点处的场强,优化得出阴极三结合点处场强值为2.55 kV/mm,阳极三结合点处场强值为23 kV/mm。     

电弧增材成形中熔积层表面形貌对电弧形态影响的仿真

电弧增材成形常采用单道多层或多道搭接的熔积方式,不同的熔积方式下对应的熔积层表面形貌不同,从而影响电弧的形态及其传热传质过程.本文建立了纯氩保护电弧增材成形的电弧磁流体动力学三维数值模型,以及不同表面形貌的熔积层模型,并在保持阳极与阴极之间距离和熔积电流不变的条件下,通过模拟计算获得增材成形特有的单道和多道搭接熔积条件下的不同表面形貌对应的电弧形态以及相应的温度场、流场、电流密度、电磁力、电弧压力分布.数值模拟结果表明:平面基板上起弧情况下电弧中心具有较高的温度、速度、电流密度以及压强;单道多层熔积情况下熔积层数对电弧的各个参量影响较小;多道搭接熔积情况下电弧呈非对称分布,电弧中心温度较前两者低,电流密度、电磁力和电弧压强的分布偏向熔积层一侧.     

On the State of Ionization,Non-Ideality and Electric Conductivity of the Cathode Plasma of Vacuum Arcs

The cathode spot plasma of a metal vapour are in vacuum has a high density (10²⁵–10²⁸ m³) with a relatively low temperature (1–5 eV), therefore it is strongly non-ideal. The degree of ionization α and the electric conductivity σ of such plasmas are discussed, considering that non-ideality. The burning voltage of the arc U_B is estimated with the help of σ-values, obtained from theories and measurements for non-ideal copper plasmas. It is shown, that a high current density of the cathode spot of j = 10¹² A/m² is not in contradiction to a low burning voltage U_B = 20–30 V, but these values give a consistent picture of the spot processes.     

Formation dynamics of bipolaron in a metal/polymer/metal structure

Charge injection process from metal electrode to a nondegenerate polymer in a metal/ polymer/ metal structure has been investigated by using a nonadiabatic dynamic method. We demonstrate that the dynamical formation of a bipolaron sensitively depends on the strength of applied electric field, the work function of metal electrode, and the contact between the polymer and the electrode. For a given bias applied to one of the electrode (V₀) and coupling between the electrode and the polymer (t^′), such as V₀=0.79 eV and t^′=1 eV, the charge injection process depending on the electric field can be divided into the following three cases: (1) in the absence of the electric field, only one electron tunnels into the polymer to form a polaron near the middle of the polymer chain; (2) at low electric fields, two electrons transfer into the polymer chain to form a bipolaron; (3) at higher electric fields, bipolaron can not be formed in the polymer chain, electrons are transferred from the left electrode to right electrode through the polymer one by one accompanying with small irregular lattice deformations.     

General intense electron beams by means of a contracted arc discharge

Two types of contracted arc discharge are investigated with a view to generating intense electron beams over a wide pressure range (1–10^–3 Pa). For an arc discharge with a hollow cathode and anode, an electron beam corresponding to a current of up to 300 A and a pulse length of 25 µsec is obtained at a pressure of 1–10^–1 Pa in the accelerating gap with an accelerating voltage of up to 15 kV. At pressures of 10^–2–10^–3 Pa, emitting plasma is created by a low-pressure arc discharge on the basis of a Penning cell. Three discharge systems operating in parallel are used to increase the working life of the cathode and improve the current density distribution of the beam. An electron beam of diameter 200 mm with a current of up to 125 A and a pulse length of 50 µsec is obtained.Institute of High-Power Electronics, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshkikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 76–82, March, 1994.     

Analysis of a hollow-cathode reflex discharge in a hydrocarbon flow

Variation of parameters of a reflex discharge with a hollow cathode operating continuously in propane with a flow rate of 1.3–5.6 (m³ mPa)/s and a discharge current of 0.1–0.4 A is analyzed. It is shown that for a hydrocarbon flow rate of 2.4 (m³ mPa)/s and higher, an increase in the discharge voltage takes place after a time interval depending on the discharge current and gas pressure; this is explained by the formation of coating of the dissociation products of hydrocarbon molecules on the electrodes of the discharge chamber. An increase in the thickness of the carbon coating of the cathodes with time and their charging with ions lead to electric breakdown of coatings and the formation of cathode spots. The oscillograms of the discharge current and voltage indicate a short-term transformation of the glow discharge into the arc discharge. The energy spectra of ions emerging from the discharge are measured, and the effect of the discharge current and the gas flow rate on the energy spread of ions is analyzed. The operation time of the discharge in hydrocarbon after which the cleaning of the discharge chamber is required is determined. The possibility of using an ion source based on the reflex discharge with a hollow cathode for technological purposes is established.