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A correction in the transit time of electrons between the filaments and the electrodes leads us to reattribute the remote unloading to ions rather than to electrons. The experimental results reported in [Opt. Express 23, 286407 (2015)] about remote electrical unloading and discharge suppression, as well as the analogy with the analogy with a supercorona, remain valid.
© 2017 Optical Society of America
1. Discussion
In the discussion of [1], we erroneously converted the 104 m/s drift speed of the electrons into a 1 μs transit time through the L = 10 cm gap between the filament and the electrodes. The correct transit time of 10 μs is well beyond the electron lifetime, preventing them to reach the electrode and ensure the conduction, at least in a streamer at a temperature close to ambient. As a consequence, their distribution cannot be modelled as an exponential decay between the filament and the electrodes, so that Eq. (3) is irrelevant and electrons cannot ensure the observed remote unloading under the experimental conditions of [1].
Rather, the ions have a mobility of 2 × 10−4 m2/Vs [2], hence a drift speed 10 m/s under an electric field of 50 kV/m. Therefore, they transit in 10 ms. After that time, their concentration is still 2 × 1019 m−3 according to the plasma model described in [3]. This ion density is sufficient to ensure the observed conductivity of several tens of GΩ [1], a conclusion consistent with recent results on electric probing of filaments [4]. However, in the case of large electric fields leading to a leader-like regime [5], a contribution of the electrons along with the ions may still be considered.
References and links
1. E. Schubert, D. Mongin, J. Kasparian, and J.-P. Wolf, “Remote electrical arc suppression by laser filamentation,” Opt. Express 23, 28640 (2015). [CrossRef] [PubMed]
2. X. M. Zhao, J.-C. Diels, C. Y. Wang, and J. M. Elizondo, “Femtosecond ultraviolet laser pulse induced lightning discharges in gases,” IEEE J. Quant. Electron. 31, 599–612 (1995). [CrossRef]
3. E. Schubert, J.-G. Brisset, M. Matthews, A. Courjaud, J. Kasparian, and J.-P. Wolf, “Optimal laser-pulse energy partitioning for air ionization,” Phys. Rev. A 94, 033824 (2016). [CrossRef]
4. P. Polynkin, “Mobilities of and ions in femtosecond laser filaments in air,” Appl. Phys. Lett. 101, 164102 (2012). [CrossRef]
5. T. Fujii, M. Miki, N. Goto, A. Zhidkov, T. Fukuchi, Y. Oishi, and K. Nemoto, “Leader effects on femtosecond-laser-filament-triggered discharges,” Phys. Plasmas 15, 13107 (2008). [CrossRef]