Experiments on the diameter of positive streamers in air

Streamer propagation and branching depends on several factors like the electrode geometry or the pressure. The influence of four different parameters on the streamer diameter (external seriesresistance, electrode gap length, pressure and voltage) is investigated. Streamer diameters are determined from images of an intensified CCD-camera. The addition of a series-resistance or a change in electrode gap length does not influence the diameter. The diameter increases with increasing voltage. Pressure and diameter are approximately inversely proportional as expected from theoretical arguments.