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The objective of this paper is to compare the state of cathode surface of different axial magnetic field (AMF) contact systems (CSs) during arcing and after arc extinction. The arcs were ignited by opening of electrodes and were fed by sine half-wave current pulses with a duration of 10 ms. Investigations were performed in the range of arc currents up to the levels of guaranteed failure. The measurements were done by a high-speed Phantom M310 video camera. The cathode surface state during arcing was studied using a set of neutral density filters. It was discovered that melting of a part of the cathode surface during arc burning takes place in high-current vacuum arcs. A changing relief in the form of hillocks and hollows forms on the melted surface. We found out that there are two components in droplet erosion of the cathode, when its surface is partially melted: in addition to droplets formed directly in the cathode spot (which can be called droplets of the first type), the liquid part of the surface also emits droplets (which can be called droplets of the second type) significantly different in their sizes and velocities. The formation mechanisms of droplets of the first and the second type are different. The cathode surface temperature distribution immediately after current zero was obtained by comparing the results of cathode surface filming to the results of calibrated band-lamp filming in identical conditions. Reflection of anode radiation from cathode surface was analyzed by mathematical simulation. The filming was carried out using an interference filter. We found that the distribution of the cathode surface temperature is substantially nonuniform. The axial region is the most heated. We conclude that in all investigated CSs with the same amplitude value of the current, the temperature of the most heated parts of the cathode surface is significantly lower than the temperature of the most heated parts of the anode surface. Analysis of obtained results shows that switching failure can be provoked by the cathode and by the anode processes depending on CS design. [ABSTRACT FROM AUTHOR]

The aim of this paper is to compare the state of anode surface of different AMF contact systems during arcing and after arc extinction. Arcs were ignited by opening of electrodes and were fed by sine half-wave current pulses with durations of 10 ms. CuCr electrodes were used. We performed investigations in the range of arc currents from successfully interrupted ones up to the levels of guaranteed failure (limiting interrupted current) if the transient recovery voltage was applied. The measurements were implemented by a high-speed Phantom M310 video camera equipped with a Carl Zeiss 100/2 macro lens. We studied the anode surface state during the arcing using the set of neutral density filters. We found that at currents close to the limiting interrupted current, most of the anode surface melts. Liquid metal is squeezed out of the axial area and an annular crest is formed. The crest splashes out and breaks into separate jets. The jets are broken up into fragments, from which droplets separate. The anode surface temperature distribution just after current zero was obtained by comparison of the results of anode surface filming and the results of calibrated band-lamp filming in identical conditions. We carried out the filming using an interference filter (775 nm). The effect of reflection from electrodes was evaluated using mathematical simulation. The temperature distribution of the anode surface is highly non-uniform. The temperature of the most heated fragments of the anode surface increases with increasing current and reaches 2000 K with the limiting interrupted current. However, the size of these fragments is small, substantially less than the length of the interelectrode gap. They cannot create the vapor concentration in the entire gap up to the opposite electrode sufficient to provide the Townsend breakdown of the gap when the transient recovery voltage is applied. The analysis of the obtained results suggests that droplets, and hence, the phenomena on the surface that lead to their appearance play an important role in the breakdown process in the investigated contact systems at extreme currents. [ABSTRACT FROM AUTHOR]

A multi-phase AC arc plasma has been applied in the glass melting technology as a promising heat source. The electrode erosion of the multi-phase arc is one of the most important issues to be solved. In the present work, the high-speed camera system with appropriate band-pass filters was applied to visually observe the dynamic behavior of the electrode metal vapor in the arc on millisecond time scale. By using this system, the evaporation of 2%-thoriated tungsten electrode was visually observed at the anodic period in the case of the 12-phase arc, while electrode evaporation is negligible in the 2-phase arc. High-speed observation of the oxygen entrainment in the arc was also carried out. Results indicated the ambient oxygen is entrained into the arc more easily with increasing the number of the phases. As a result, the electrode evaporation becomes more severe with larger number of the phases.

Low-current Townsend discharge in nitrogen has been studied in the temperature range of T = 100-300 K in a semiconductor-gas-discharge structure. It was found that the sustaining voltage US increases with time when a current is passed through the structure at low T. This effect was not observed at room temperature. A hypothesis is put forward that a film of a neutral phase of nitrogen is formed on the electrodes under cryogenic discharge conditions. The presence of the condensed thin-film phase leads to a decrease in the secondary electron emission from the electrode and to a corresponding increase in US. A possible mechanism of the phenomenon is associated with the formation of large neutral aggregates in the form of [N+2(N2) n]- in the gas discharge volume. The condensation of these aggregates seems to yield a phase that is comparatively stable at cryogenic temperatures (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Electrodialysis (ED) is an electrochemical separation process by which electrically-charged species are transportedfrom one solution to another ED is a combined method of dialysis and electrolysis and can be performed with two main cell types: multi-membrane cells for dilution-concentration and water dissociation applications (membrane phenomena), and electrolysis cells for redox reactions (electrode phenomena). The dilution-concentration principle applications in the dairy industry consist mainly of the demineralization of milk or milk by-products. The use of ED with monopolar membrane for protein separation and acid caseinate production, and in bioreactors for organic acid production, is also studied in the dairy industry. The interest of ED as a membrane process has been triggered recently by the development of a new membrane type, bipolar membrane. This membrane carries out the dissociation of water molecules. ED with bipolar membranes was applied very recently to the production of lactic acid from whey product fermentation, production of caseinates, and fractionation of whey proteins. Two principle applications of electrode reactions were published: electrochemical coagulation (EC) to precipitate milk proteins, and electroreduction for the reduction of disulfide bonds in the proteins. It appears in this article that processes using membrane phenomena are more numerous and developed than electrolytic applications. This is the composition of milk and the lack of knowledge of redox reactions of the different food compounds that limit the applications and the development of electrolytic phenomena. Electrodialytic phenomena present a great potential for application in the dairy industry, and more generally, in the food industry; many of these applications have to be discovered. [ABSTRACT FROM AUTHOR]

Traces the history of the first 40 years of the International Symposia on Discharges and Electrical Insulation in Vacuum. First symposia held in October 1964 at Cambridge, Massachusetts; History of the Permanent International Scientific Committee (PISC); Presentation formats; Value to participants; Awards; Developments in techniques used in papers presented at the symposia; Developments in the fields of the symposia.

Abstract: Comparison is made among electrode-related ion dynamics in gold-anoded glass samples of AgPO3, NaPO3, and Na2O–2B2O3 to biasings with a DC pulse train, measured at respective temperatures at which ionic conductivities are the same, 2×10−5 S/cm. It is found that the response is strongly dependent on the temperature; that is, the higher the temperature, the more easier is the formation of the positive and negative ion-depleted region underneath the anode by which the conduction current decays with time. Intermittent biasings enable us to see shuttling motion of the positive ions, moving toward the cathode on biasing but moving in the reverse direction on off biasing. [Copyright &y& Elsevier]

Electrodialysis (ED) is an electrochemical separation process by which electrically-charged species are transported from one solution to another. ED is a combined method of dialysis and electrolysis and can be performed with two main cell types: multi-membrane cells for dilution-concentration and water dissociation applications (membrane phenomena), and electrolysis cells for redox reactions (electrode phenomena). The dilution-concentration principle applications in the dairy industry consist mainly of the demineralization of milk or milk by-products. The use of ED with monopolar membrane for protein separation and acid caseinate production, and in bioreactors for organic acid production, is also studied in the dairy industry. The interest of ED as a membrane process has been triggered recently by the development of a new membrane type, bipolar membrane. This membrane carries out the dissociation of water molecules. ED with bipolar membranes was applied very recently to the production of lactic acid from whey product fermentation, production of caseinates, and fractionation of whey proteins. Two principle applications of electrode reactions were published: electrochemical coagulation (EC) to precipitate milk proteins, and electroreduction for the reduction of disulfide bonds in the proteins. It appears in this article that processes using membrane phenomena are more numerous and developed than electrolytic applications. This is the composition of milk and the lack of knowledge of redox reactions of the different food compounds that limit the applications and the development of electrolytic phenomena. Electrodialytic phenomena present a great potential for application in the dairy industry, and more generally, in the food industry; many of these applications have to be discovered. [ABSTRACT FROM AUTHOR]