Low jitter, high current spark gap operating with air at normal pressure
Résumé
oral presentation. We demonstrate a simple, reliable air spark gap operating at atmospheric pressure and able to switch currents in excess of 10 kA. The spark gap with an interelectrode spacing close to10 mm is remotely triggered by a femtosecond laser system. This laser delivers pulses at 800 nm of typically 350 fs duration and energy of 200-250 mJ, corresponding to a peak power of about 600 GW. After propagation in air, the weakly converging laser beam undergoes filamentation. This leads to the production of a 1-2 m long continuous plasma column of nearly uniform longitudinal electron density n ~ 1016 electrons/cm3. The plasma column of diameter ~ 5 mm connects quasi instantaneously to electrodes. We studied two switch configurations. In first one two cylindrical electrodes of diameter 36 mm pulse charged up to 0.6-1.2 of the self-break voltage (25-30 kV). The triggered laser beam passes through holes 3 and 5 mm diameter. A sub-nanosecond jitter is demonstrated. The second configuration consists of spherical metal electrodes of 10 and 20-mm diameter DC-charged. They are connected to the laser produced plasma channel by grazing contact with vertical electrode shift of 2-3 mm. Jitter of 1-3 ns have been measured here.