Evolution Of A Laser Filamentation Triggered Electric Discharge In Air

Summary form only given. Laser filamentation guided electric discharges have many interesting applications, among which are the laser lightning rod, plasma aerodynamic control, high-power closing switches and plasma antennas. The latter cases rely on a precise control of the discharge plasma lifetime, either to adapt the switch or antenna on-state time to the current situation. In this work, we study the link between the temporal evolution of a laser filamentation triggered discharge plasma column and the discharge current waveform. The centimeter long plasma is generated by the discharge of a 2 nF capacitor charged to 15 kV, yielding a constant electric energy of 200 mJ. Various ballast resistances ranging from 400 to 10 Ω allow modifying the current waveform in the monopolar regime. A 29 μH coil can also be used to bring the circuit in the oscillatory regime. Plasma is characterized by means of two-color interferometry, enabling us to extract space and time-resolved electron density and neutral density radial profiles. We found that, in the monopolar regime, as the current pulse amplifies and shortens, electron density decay becomes dominated by electron-ion recombination, while low-current impulses result in a plasma decay closely related to the current waveform. Longer plasma lifetime is achieved using strong and short current pulses. As for the oscillatory regime, we show that in this case the plasma has a very slow decay, resulting in more favorable conditions for the generation of long lived plasma columns.