Control of extended high-voltage electric discharges in atmospheric air by UV KrF-laser radiation

Experiments in the commutation of extended (~1-m long) high-voltage (up to 390 kV) electric discharges were carried out with the aid of 100-ns long UV pulses of the GARPUN KrF laser, in which we demonstrated a one-and-a-half-fold lengthening of the discharge gap broken down in the presence of laser illumination. Total control of discharge trajectory along the direction of the laser beam was observed for a radiation energy of ~300 mJ (the corresponding intensity I = 5×10⁸ W cm^-2 and its attendant initial electron density Ne ~10¹¹ cm^-3) and partial control for an energy of 40 mJ (I = 7×10⁷ W cm^-2, Ne ~8×10⁹ cm^-3) with a 100% probability of breakdown. We discuss the advantages of employing a UV laser for active lightning protection in comparison with IR lasers and ultrashort-pulse laser systems.