Temperature Measurements In A Welding Arc By Rayleigh Scattering And Emission Spectroscopy

Consecutive Rayleigh scattering and emission spectroscopic measurements have been performed on an atmospheric argon Gas Tungsten Arc Welding (GTAW) torch, at 100 Amperes and 5mm electrode-gap spacing, burning over a copper chilled block. Rayleigh scattering measurements (published elsewhere*) taken with a pulsed Nd:YAG laser at four different axial locations (0.5, 1.5, 2.5 & 3.5 mm above the anode) show scattering intensity profiles that decrease again to a peak value at the center of the arc. Assuming that the scattering signal is predominantly due to ground-state Rayleigh scattering cross-sections, heavy particle temperatures, calculated from Dalton's law, yield reasonable values up to 8000 ^°K in the arc fringes; however, under the same assumption, high scattering intensity values in the arc center yield unrealistically low temperatures down to 400 ^°K in the core of the arc. The high scattering intensity in the core of the arc may be caused by near resonance scattering or by the charged particles.