A comprehensive experimental examination of the interaction between a subsonic thermal plasma jet and injected alumina particles is presented. Measurements of plasma velocity, temperature, and entrained air were obtained from an enthalpy probe and mass spectrometer combination. A diffusive separation, or demixing, of the Ar and He plasma gas was observed Centerline plasma velocities and temperatures ranged from 150-1500 m/s and 2000 to 14,000 K, respectfully, in the region between the torch and a typical substrate location of 90 mm. Measurements of particle size, velocity, temperature, and local number density were obtained from a combination laser particle sizing system, Laser doppler velocimeter (LDV), and two-color pyrometer. Centerline temperatures and velocities for the nominally 30 mu m particles used weve 2400-2800 K and 150-200 m/s, respectively.