Determination of gas-temperature and velocity profiles in an argon thermal-plasma jet by laser-light scattering

Gas-temperature and velocity profiles at the exit plane of a thermal argon plasma torch have been determined directly from a high-resolution Doppler-shifted line-shape analysis of laser light scattered by the plasma. Peak temperature and velocity values observed were 13 350 K±7% and 1100 m s -1 ±3%. Velocities as low as 45 m s -1 ±45% were measured in the fringe of the jet. An injection-seeded pulsed neodymium-doped yttrium aluminum garnet laser was used as the laser source and the scattered laser light was analyzed with a scanning tandem Fabry-Perot interferometer. Temperature data obtained from laser scattering are compared with values obtained from emission spectroscopy and show a severe departure from local thermodynamic equilibrium (LTE) in the outer regions of the jet