Strahlungstransportmechanismus und Transportkoeffizienten im Ar-Hochdruckbogen

Abstract

TheE(J)-characteristics, the total radiated powerU(J), and the radial temperature distributionsT(r, J) measured in a 5 mm diam. Ar cascade arc between 1 and 10 atms are used to evaluate the transport properties of Ar with special attention to the radiation transport mechanism. The electrical conductivity σ(T,p) is determined from the characteristics and temperature distributions by means of Ohm's law. Comparing the results with Langevin's formula, the cross-sections for electron-ion and electron-atom collisions are calculated. The transparent emission coefficiente _tr (T, p) in the transmission range of quartz is extracted in a similar way from the radiation characteristicsU(J); its continuum contribution, which amounts up to 90%, is obtained by integrating the measured spectral continuum distribution. Inserting σ(T, p)E ² ande _tr (T, p) into the energy balance yields the thermal conductivityk _therm (T,p) as well as the uv radiation contribution. The latter can be described by ordinary radiation diffusion above 3 atms and by long range radiation at atmospheric pressure. So the electric power supplied to the arc leaves it in radial direction partially by heat conduction, partially by transparent radiation in the visible and adjacent spectral regions, and partially by ordinary radiation diffusion in the far uv atp≧ 3 atms or by long range diffusion at about atmospheric pressure.