Triggering and guiding high-voltage large-scale leader discharges with sub-joule ultrashort laser pulses

The triggering and guiding of leader discharges using a plasma channel crea ted by a sub-joule ultrashort laser pulse have been studied in a megavolt l arge-scale electrode configuration (3-7 m rod-plane air gap). By focusing t he laser close to the positive rod electrode it has been possible, with a 4 00 mJ pulse, to trigger and guide leaders over distances of 3 m, to lower t he leader inception voltage by 50%, and to increase the leader velocity by a factor of 10. The dynamics of the breakdown discharges with and without t he laser pulse have been analyzed by means of a streak camera and of electr ic field and current probes. Numerical simulations have successfully reprod uced many of the experimental results obtained with and without the presenc e of the laser plasma channel. (C) 2001 American Institute of Physics.