An experimental investigation of nonequilibrium effects in wall-confined argon plasma arcs

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Abstract
Deals with thermal equilibrium between the particles in argon plasma arcs. The current limit for LTE is experimentally defined as a function of the pressures. Plasma parameters were spectroscopically determined. In particular, the electron temperature and heavy particle temperature were measured. The electron temperature was determined from an absolute continuum strength. Two temperatures were obtained for the heavy particles, one of which was determined from the Doppler component of the Halpha line when argon gas seeded with hydrogen was used. The second was obtained through a kinetic formula using the measured density and temperature of the electron. The results show that the electrons did not equilibrate with the heavy particles at low currents and pressures. The limit value of the current for LTE increased with decreasing gas pressure. It is shown, furthermore, that the measured field strength of the arc was remarkably lower than those calculated at currents less than the above limits.
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