Velocity distribution of carbon macroparticles generated by pulsed vacuum arcs

The velocity distribution of carbon macroparticles have been measured using a simple optical technique with a gated charged-coupled device camera, ultilizing the lightemitted by the incandescently bright particles. Distributions have been separately determined for macroparticles which have and have not experienced collisions with a solid wall (the anode). The measured velocities are in the range 10-370 m s-1. The distribution without wall collinsions peaks at 80 m s-1, while the distribution of particles with wall collisions peaks at about 50 m s-1. This indicates that, in the average, about one-third of the kinetic energy islost to the wall when a collision occurs, assuming macroparticles remained intact. However, it is shown that most carbon macroparticles fracture into even smaller particles when colliding with a surface. The velocity measurements do not include either very small (submicrometre) or cooled-off particles.