Spectroscopic measurements have been made on a transferred arc burning in pure argon at atmospheric pressure seeded with iron vapours arising from the anode erosion. The transferred arc was operated with a current intensity of 90 A, an arc length of 18 mm, and a gas flow rate of 8 l min −1 . Temperature and relative iron concentration profiles determined experimentally were compared to theoretical values obtained from a two-dimensional model based on mass, momentum, and energy conservation equations and taking into account anode erosion. This comparison partially validated the model and showed that the presence of iron vapours, with a relative concentration of about 0.1%, led to a temperature decrease of about 1000 K. Differences between experimental and calculated temperature fields may be due to departures from equilibrium and to uncertainties about the iron vapour concentration and the radiative losses.

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This study into radiative transfer in a arc plasma is devoted first to measure the relative absorption of the arc radiation by cold gas; second, to calculate this absorption; and third, to obtain a simplified expression for this absorption useful in arc modelling. In general, more than 50% of the radiation emitted by a arc is absorbed in the surrounding gas.