Ionization wave propagation in long tube discharges

Summary form only given. We describe observations of ionization wave propagation during the starting of long tube, rare gas discharges. Particular emphasis is placed on how the discharge tube internal surface conditions and wall curvature influence wave propagation velocity. The starting of a discharge with large length to diameter ratio occurs in several steps. A free electron must be generated which then initiates an avalanche, typically near the cathode. The resulting avalanche produces a conductive plasma which charges up the long tube´s insulating wall in the electrode region. The localized wall charging launches an ionization wave which bridges cathode to anode with a conductive path, after which the discharge starts. Wall properties influence charge production and loss and thus affect wave propagation.