Prolongation of the lifetime of guided discharges triggered in atmospheric air by femtosecond laser filaments up to 130 μs

Abstract

Abstract:The triggering and guiding of electric discharges produced in atmospheric air by a compact 100 kV Marx generator is realized in laboratory using an intense femtosecond laser pulse undergoing filamentation. We describe here an approach allowing extending the lifetime of the discharges by injecting a current with an additional circuit. Laser guiding discharges with a length of 8.5 cm and duration of 130 µs were obtained.In the last decade femtosecond laser filaments has proved to be a powerful tool to trigger and guide electric discharges in atmospheric air 1 with gap length of a few meters [2][3][4][5][6] . The weakly ionized plasma column and subsequent low density channel generated by laser filaments allow the precise triggering and guiding of electric discharges between two electrodes with a significant reduction of the breakdown voltage [7][8][9] . This effect is potentially useful for the development of laser lightning rod 4, 10-11 , high-voltage, high-current switches 12 , or virtual plasma antennas [13][14] .For applications such as plasma antennas, extension of the filament plasma lifetime is needed, since the plasma from the filament recombines in a few nanoseconds, seriously limiting the bandwidth of antennas to frequencies v> 10 9 Hz. This can be done using additional femtosecond or nanosecond laser pulses 15-17 but this technique is particularly complex and the resulting plasma is limited to a few µs. Injection of electric current through guided discharges appears to be a more promising way. The duration of the guided discharge mostly depends on the high voltage (HV) source, with a typical duration on the order of 100 ns [2][3][4]14 . In several publications, a Marx generator was used as the HV source to produce meter scale guided discharges. In this case, the discharge duration is defined by the product of the Marx "stack" capacitance C marx and a discharge load R load . In Ref. 18, a compact Marx generator was used to create a ~ 21 cm guided discharge of duration about 600 ns due to the mentioned Marx capacitance C max ~ 2 nF and the discharge load resistance R d ~ 300 Ω. In this letter we describe a method, which allows prolonging this parameter up to 130 µs. The experiment setup is presented in Fig. 1. The circuit is composed of two parts. The first part is a Marx generator described in 18. For this experiment the generator was composed of 5 stages charged up to 20 kV DC, resulting in 100 kV output pulse with a negative polarity. An inductance L 1 was connected to the generator output electrode and served as a load up to the moment when the Marx pulse produces a breakdown in the inter-electrode gap. The Marx output electrode has a cylinder form with an axial hole allowing the laser beam to enter in the generator and to trigger it. The second electrode is a round finger with a 5 mm radius. As described in Ref. 18, a chirped pulse amplified laser system emitting at a wavelength of 800 nm is used to produce the filaments between the two electrodes and inside the Marx generator. The laser pul...

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

“…Recent works succeeded to increase the laser-produced plasma lifetime up to few microseconds by using an external electric field from a 50 kV DC high-voltage source19. In addition, other work recently reported an increase of the laser-guided discharge lifetime up to 130  μ s by inserting inductances on a 100 kV Marx generator20.…”

Long-lived laser-induced arc discharges for energy channeling applications

“…The generation of millisecond-duration, 100 A sparks was done using a slightly modified version of the double-circuit scheme already used by Arantchouk et al . 25 . This scheme was built around a filamentation-triggered Marx generator as the high-voltage source.…”

“…also demonstrated control of curved spark trajectories by means of Airy laser beams instead of the widely used Gaussian beam 24 . Théberge and co-authors also showed that meter-sized, milliseconds duration guided discharges can successfully be developed using a double-circuit scheme 25 , 26 .…”

Note: Investigation of a Marx generator imitating a Tesla transformer

“…Using this with (7), the circuit parameters may be estimated using L, (8)(9)(10)(11), and the fit parameters α i and ω i as…”

“…Such modified Marx generators are shown to tolerate circuit-parameter changes more than Tesla transformers, making them attractive alternatives to Tesla transformers in the applications mentioned above. While compact, 13 high-repetition, 14 and inductively loaded 9 Marx generators and coupled Marx-Tesla circuits 15 exist, this work demonstrates that a modified a) Present address: Facebook, Inc., 1 Hacker Way, Menlo Park, CA 94025, USA Marx generator can mimic a conventional, loosely coupled spark-gap Tesla transformer (SGTT). Fig.…”