Temperature measurement of asymmetrical pulsed TIG arc plasma by multidirectional monochromatic imaging method

Abstract

Arc plasma diagnostics by spectroscopy have been often used to measure the arc properties, such as the temperature. Measurements of an axially asymmetrical arc plasma require the optical computed tomography technique. This study constructed the simultaneous and multidirectional measurement system by six sets of CCD camera and interference filter with monochromatic imaging method. The deviation of the central wavelength of the filters was calibrated by tilting operation, and the sensitivity of detectors was calibrated by referencing the stationary and axially symmetric tungsten inert gas (TIG) arc plasma. We could perform the temperature measurement of the transient and asymmetrical TIG arc plasma such as in the transition period between the peak 150 A and base 10 A current of a 50 Hz pulsed TIG arc with 30° tilted torch. It was revealed that the high-temperature area of 30° tilted arc is larger than that of perpendicular arc. The comparison of pulsed and continuous arcs shows that the arc shape and the temperature variation reasonably followed the current change as long as the changing rate was about −113 A/ms.