Time and spatially resolved spectroscopic measurement of temperatures in a free-burning arc by monochromatic imaging

An imaging method that involves a high-speed camera and a narrow-band filter has been used to acquire images of the argon atomic line intensity of a free-burning arc plasma at atmospheric pressure. The measured lateral intensities are converted to radially distributed emission coefficients by means of an Abel inversion. Under the assumption of local thermodynamic equilibrium, the time resolved temperature distributions in the arc have been determined. Both the intensities and temperatures indicate that the arc was gradually evolving toward a static state after it was ignited; the temperature at any position of the arc column shows the same decreasing trend. These results demonstrate that this method enables the time and spatially resolved properties of plasmas to be characterized and thus it may bring new findings and applications concerning the diagnostics of plasmas.