Transport velocities of particles in the plasma of a d.c. arc in air

Axial transport velocities of materials injected into a d.c. arc plasma by a liquid jet method have been determined on the assumption that the motion is influenced by diffusion (due to gradients in the number density of particles), axial electric field and convection. The velocities were measured using both high speed cinematography and cross-correlated photomultiplier signal techniques. In the interpretation of the measurements, with both methods use had to be made of the motion of the constant concentration boundary of the injected material in the frames of reference relative to both the arc electrodes and the point of maximum material density. Particular attention was given to convection effects.