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[en] The development of concepts of anode phenomena in arc discharges in a gaseous medium over a wide pressure range, as well as in vacuum arcs, is discussed. The current state of these investigations is analyzed. Various forms of attachments of the arc to the anode and the results of experimental and theoretical investigations of these attachments are described. Considerable attention is paid to investigations of the conditions and causes of transitions between the different forms of attachments-diffuse and contracted. (topical review)
[en] In the field of non-thermal plasmas, the term 'high pressure' generally refers to pressures ranging from 0.01 to 0.1 MPa. For pressures higher than 1 MPa, the behaviour of low-current electrical discharges remains a poorly explored area. However, the study and the control of such discharges can open new prospects in many application fields such as chemistry, lighting or material synthesis. This paper reports an experimental analysis of a tip-tip electrical discharge supplied with dc voltage in a pure helium atmosphere at high pressures. The electrical characteristics of the discharge are analysed for pressures ranging from 0.1 to 15 MPa, for currents ranging from 250 to 400 mA and inter-electrode gaps ranging from 0.25 to 2.5 mm.
[en] A simplified linear analysis for resistive-viscous magnetic helical instabilities of arc discharges in a cylindrical plasma is developed. Based on a set of electrostatic magnetohydrodynamic (MHD) equations, resistive-viscous m=1 modes with an external axial magnetic field are studied. Explicit analytic results are obtained, from which the growth rate and the stability criterion can be shown, and the electrostatic assumption can be justified. In comparison with the previous channel model calculations, this analytic treatment can provide a simplified model for instability estimates, while avoiding artificial assumptions and misorderings in the energy equation. copyright 1997 American Institute of Physics
[en] The device shall ensure the reliable ignition of long arcs in any gas without causing leakages, short circuits or voltage losses between electrodes and auxiliary electrodes, that might disturb or prevent ignition. Thermal overload of the auxiliary electrodes as well as stray currents are prevented by automatic disconnection of the device after arc ignition. The device is applicable in plasma technology, especially to gas heating and plasma chemistry