The scaling of the streamer-to-arc transition in a positive point-to-plane gap with pressure

The sequences primary streamer-secondary streamer-arc transition are investigated in a positive point-to-plane electrode configuration for air pressure P in the range 1 to 10 bar. The evolution of the current and the emitted light during the predisruptive sequences are similar, whatever the pressure value, if the usual scaling factor Pd (but also P rho , rho being the point radius) and the applied positive potential remain constant. It was observed that the primary streamer velocity and product TP, T being the time between two discharges, remain constant. The anomaly of the decrease in the current was understood in terms of hydrodynamic phenomena which are more influential at high pressure than at atmospheric pressure.