The development of single streamers started by laser light at high overvoltages in rare gases

Investigations on the temporal development of single streamers performed with an electro-optical streak camera are reported. The starting electrons being released by the focused radiation of a giant-pulse ruby laser, any influence of the electrodes can be excluded. In rare gases the propagation of streamers was observed in a homogeneous field (gap distance 11 cm), beginning from low E/p and up to higher E/p corresponding to overvoltages of several hundred per cent. The velocities of different streamer stages are measured. Below a certain E/p value they are relatively low (some 10 8 cm s −1 ) and proportional to E/p . Above this value, a considerable increase in streamer velocity up to 5 × 10 9 cm s −1 is observed.