Threshold Conditions for Terahertz Laser Discharge in Atmospheric Gases

Kubarev, V. V.; Getmanov, Ya. V.; Shevchenko, O.A.; Koshlyakov, P. V.

doi:10.1007/s10762-017-0380-3

Cited by 21 publications

(25 citation statements)

References 14 publications

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“…The peak power density of the incident beam to the parabolic mirror was accordingly estimated as 33 kW/cm 2 , which corresponds to an intensity of 5.0 kV/cm as the oscillating electric field. Assuming the beam radius of λ at the focal point 26 , the average beam intensity reaches to 51 kV/cm. This value is safely larger than the critical intensities estimated above.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Observation of a comb-shaped filamentary plasma array under subcritical condition in 303-GHz millimetre-wave air discharge

Fukunari

Tanaka

Shinbayashi

et al. 2019

Sci Rep

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Gas breakdown in the millimetre-wave frequency band is an interesting phenomenon in nonlinear dynamics such as self-organized structure formation. We observed the transition between two types of filamentary plasma arrays in air discharge driven by a 303-GHz millimetre wave. Plasma is ignited at a parabolic mirror’s focal point in the overcritical condition. One array parallel to the electric field vector appears with a spacing of λ/4 at the focal point. Filaments then separate into plasma lumps ~10 μs after ignition. At 20 μs, a new comb-shaped array grows in the subcritical condition. Filaments are parallel to the incident beam with spacing of 0.96 λ and elongate towards the incident beam. This comb-shaped array appears only in the electric field plane; bulk plasma with a sharp vertex forms in the magnetic field plane. This array is created by a standing wave structure generated by waves diffracted from the plasma surface. Filamentary plasma array formations can influence the energy absorption by the plasma, which is important for engineering applications such as beamed energy propulsion.

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Section: Experimental Apparatusmentioning

confidence: 99%

Observation of a comb-shaped filamentary plasma array under subcritical condition in 303-GHz millimetre-wave air discharge

Fukunari

Tanaka

Shinbayashi

et al. 2019

Sci Rep

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“…A principal difference of argon, which has a minimum breakdown threshold of 1.1 GW/cm 2 , from other gases (helium, air, nitrogen, or carbon dioxide) was the transformation of the discharge breakdown stage with a minimum plasma content into an intense laser-plasma discharge, in which the plasma volume and the optical radiation intensity were much larger, at a NovoFEL power exceeding the threshold breakdown values by 30-50 %. 21 In the case of air, nitrogen or carbon dioxide, no such transition was observed even at powers twice the threshold value. In the conditions of our experiment, the radiation of the gas discharges had form of a train of separate pulses, without the equilibrium plasma stage.…”

Section: Experimental Setup and Methodsmentioning

confidence: 98%

“…1) focused this beam, there appeared a Gaussian beam waist of a 0.15 mm (FWHM), the radiation intensity on the axis of the focal spot being equal to 1.6 GW/cm 2 . 21 All our experiments were carried out at atmospheric pressure. Various gases were fed through a tube ( Fig.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…According to Ref. 21, a laser breakdown of atmospheric gases was observed at radiation intensities in the range of 1.1-1.6 GW/cm 2 . A principal difference of argon, which has a minimum breakdown threshold of 1.1 GW/cm 2 , from other gases (helium, air, nitrogen, or carbon dioxide) was the transformation of the discharge breakdown stage with a minimum plasma content into an intense laser-plasma discharge, in which the plasma volume and the optical radiation intensity were much larger, at a NovoFEL power exceeding the threshold breakdown values by 30-50 %.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

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Continuous point-like high-temperature laser discharge produced by terahertz free electron laser

2017

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A continuous point-like laser discharge of record high temperature has been produced in argon at atmospheric pressure with focusing of the radiation of the Novosibirsk terahertz free electron laser (NovoFEL). According to spectral measurements, the temperature in the center of the millimeter-sized plasma sphere was 28000 K at a plasma density of 1.5×1017 cm-3 and an average NovoFEL power of 200 W at a wavelength of 130 μm (2.3 THz).

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“…The radiation is an infinite sequence of 30-100 ps pulses with a standard repetition rate of 5.6 MHz and average power of up to 100-200 W. Regimes in which the radiation is coherent are described in [3]. Such parameters enabled the development of several superfast and highresolution techniques of molecular spectroscopy [4,5], and the high pulse power allowed ignition of a continuous optical discharge in gases at the atmospheric pressure [6]. Many applications require transformation of a Gaussian laser beam into beams of different mode structure or concentration of radiation in a predetermined volume or on an area.…”

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confidence: 99%