COMPARISON OF ENTHALPY PROBE AND LASER-LIGHT SCATTERING MEASUREMENT OF THERMAL PLASMA TEMPERATURES AND VELOCITIES

Gas temperature and velocity profiles in argon thermal plasmas, measured by an enthalpy probe and high spectral resolution laser light scattering, are compared. In the laser scattering measurement the plasma temperature and velocity are determined directly from high-resolution Doppler-shifted line-shape analysis of light scattered by the plasma. The technique yields an unambiguous determination of gas or kinetic temperature without the assumption of local thermodynamic equilibrium. Velocity is determined directly from the measured Doppler shift. The enthalpy probe is a combination Pitot tube and flowing calorimeter. The assumption of thermodynamic equilibrium is required to obtain velocity and temperature from measured enthalpy and stagnation pressure. Peak temperature and velocity values observed were approximately 13 000 K and 1300 m s-1. The results from both the intrusive enthalpy probe and nonintrusive laser light scattering technique compare favorably. The limitations of both techniques are discussed.