Femtosecond laser guiding of a high-voltage discharge and the restoration of dielectric strength in air and nitrogen

Leonov, Sergey B.; Firsov, A. A.; Shurupov, M. A.; Michael, James B.; Shneider, Mikhail N.; Miles, Richard B.; Попов, Н. А.

doi:10.1063/1.4769261

Cited by 46 publications

(24 citation statements)

References 17 publications

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“…The phenomenon we have described should not be confused with the laser guiding of (streamer) discharges described by [27,28] and others, where focused high power lasers create a thin channel with an electron and ion density of 10 16 -10 17 cm −3 in atmospheric air, while the ionization inside a streamer channel amounts to 10 15 cm −3 at most. Such laser channels modify the background electric field at least one order of magnitude more rapidly than a streamer, and effectively act as conductors.…”

Section: Comparison With Other Laser Guiding Experimentssupporting

confidence: 60%

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Streamer discharges can move perpendicularly to the electric field

et al. 2014

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Streamer discharges are a primary mode of electric breakdown in thunderstorms and high voltage technology; they are generally believed to grow along electric field lines. However, we here give experimental and numerical evidence that streamers can propagate nearly perpendicularly to the background electric field. These streamers are guided by pre-ionization that is orders of magnitude lower than the ionization density in a streamer channel, hardly affecting the background field. Positive streamers could be guided in nitrogen with 0.5% of oxygen or less, but not in air. This observation also tests the role of photoionization in gas mixtures with varying nitrogen-oxygen ratio.

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Section: Comparison With Other Laser Guiding Experimentssupporting

confidence: 60%

“…Furthermore, in the other studies [28,29] the laser is usually aligned parallel to the field lines. Here we have shown that very weakly ionized regions that are almost perpendicular to the local field lines can still guide the streamers.…”

Section: Comparison With Other Laser Guiding Experimentsmentioning

confidence: 99%

Streamer discharges can move perpendicularly to the electric field

et al. 2014

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“…The amplitude of the microwave electric field in the channel for the general case of scatterers with dielectric permittivity ε and conductivity σ when channels are thin compared to skin depth ( mm for microwave frequency ~10.58 GHz use in this work) can be written as:where k - depolarization factor governed by the channel geometry, E 0 - incident microwave electric field at the channel location3233. The depolarization factor k for the channels with large aspect ratio m = l/d ≫ 1 is small: 343536.…”

Section: Methodsmentioning

confidence: 99%

Electric discharge during electrosurgery

Shashurin

Scott

Zhuang³

et al. 2015

Sci Rep

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Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 103 A/cm2. The plasma electron density and electrical conductivities in the channel were found be 1016 cm−3 and (1-2) Ohm−1cm−1, respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold.

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“…The discharge position is detected right in mixing layer of some pairs of gases involved. Finally, it was demonstrated that the discharge channel position can be effectively tailored by a little energy beam of a femtosecond laser [39]. Recently, the mixing intensification in high-speed flow due to filamentary discharge generation was experimentally proven by means of analysis of flow disturbances and measurements of local fuel concentration by method of probe breakdown fluorescence [40].…”

Section: Mixing Enhancement Experimentsmentioning

confidence: 99%

Plasma-enhanced mixing and flameholding in supersonic flow

Firsov

Savelkin

Yarantsev

et al. 2015

Phil. Trans. R. Soc. A.

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The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M = 2, static pressure P st = 160-250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of W pl = 3-24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air-fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at offdesign operation.

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Femtosecond laser guiding of a high-voltage discharge and the restoration of dielectric strength in air and nitrogen

Cited by 46 publications

References 17 publications

Streamer discharges can move perpendicularly to the electric field

Streamer discharges can move perpendicularly to the electric field

Electric discharge during electrosurgery

Plasma-enhanced mixing and flameholding in supersonic flow

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