The influence of vibrational excitation on the burning voltage of a pulsed electric discharge in HF laser working media

In this paper, the critical reduced electric fields (E/N)cr in SF6 are determined over a temperature range 298–2300 K. These fields are derived from the quasi-stationary burning voltages of a self-sustained volume discharge in SF6 irradiated by a CO2-laser through a slit diaphragm. Visualization of the shock-wave disturbances generated by the temperature jump at the boundary between the laser-heated and cold gas and measurements of the discontinuity surface propagation velocities are performed. A purpose-developed VSh method allowing determination of the gas temperature T by the shock wave propagation velocity has been proposed to evaluate the temperatures exceeding 1500 K. The (E/N)cr-values obtained at T > 2000 K are compared with those measured under the conditions of the complete thermodynamic equilibrium. The difference found is treated in terms of the authors' concept of the dielectric strength of strongly heated electronegative polyatomic gases. A number of fundamentally new physical effects are shown to arise at the discontinuity surfaces in a shock-wave-disturbed SF6 after voltage application. Some aspects of relevance to these effects are qualitatively discussed. Special attention is given to the dynamic barrier effect.

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“…The set-up used in this study is mainly analogous to that of [1,11]. Therefore only some basic points are briefly discussed.…”

Section: Methodsmentioning

confidence: 99%

The critical reduced electric fields in SF₆at high gas temperatures

Belevtsev

Firsov

Kazantsev

et al. 2008

J. Phys. D: Appl. Phys.

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“…For without outward triggering source, the delay time of electric breakdown varies from 50 ns-400 ns, the quasi-stationary voltage q U after breakdown only changes with the SF 6 gas pressure, the amplitude increases with the SF 6 gas pressure, the quantity of C 2 H 6 has no effect on q U . We found the value of the electric field intensity reduced to the unit partial SF 6 gas pressure in quasi-stationary stage E/P SF6 always keeps constant, the value equals 88.8 V/(m*Pa), It is higher than that of the TEA CO 2 laser, which is about 10 V/(m*Pa) [7][8][9] . The observations confirmed the conclusion that the voltage across the discharge gap throughout the quasi-stationary stage is independent of the initial voltage V , the electrode area and charging capacitance C , but is determined only by electrode spacing, the SF 6 partial gas pressure.…”

Section: Methodsmentioning

confidence: 84%

Volume-discharge formed in SF₆and C₂H₆mixtures without preionization

Zhang

Ke²,

Zhang

2014

SPIE Proceedings

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A new approach to obtain glow discharge in working mixtures of non-chain HF laser has been brought forward. The most advantage of the approach is without pre-ionization, so the contamination of pre-ionization will not happen and the laser equipment is compact and simple. It is found, if the cathode surface is equally rough, we can obtain uniform volume-discharge in SF 6 mixtures without any pre-ionization, and dispense with uniform electric field electrode profile. The form of Self-Sustained Volume Discharge (SSVD) is a Self-Initiated Volume Discharge (SIVD). We show here the possibility of obtaining SIVD with a uniform energy deposition in a system of electrodes with non-uniform electric field. Experiments show that, with rough cathode and even anode, a volume discharge is forming in non-uniform electric-field without pre-ionization in SF 6 and C 2 H 6 mixtures. At the beginning of the discharge, many diffuse channels attached to bright circular cathode spots, then, diverge towards the anode, with the channels overlapping, form a spatially uniform glow discharge. SIVD has been performed at a total mixture pressure up to 8kPa and energy deposition up to 200J/l. We also report measurements of the V-I characteristics of SIVD with SF 6 and C 2 H 6 mixtures at pressure up to about 8kPa. The experimental results indicate that SSVD in SF 6 and C 2 H 6 mixtures develops in the form of SIVD is promising for creation of high energy and pulse-periodic HF laser.

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“…The set-up and experimental procedures were generally identical to those of [1,10]. The set-up is schematically represented in figure 1(a).…”

Section: Methodsmentioning

confidence: 99%

“…The process of laser radiation energy deposition in SF 6 and SF 6 -based mixtures under the conditions of interest has been studied in [2,10] in greater detail. It is shown that the equilibrium between the vibrational and translation degrees of freedom has time to establish by the CO 2 laser pulse termination and, if the delay between the laser and voltage applications approaches the laser pulse duration, the initial gas temperature distribution along the axis normal to the diaphragm slit takes a rectangular form with a maximum in the irradiation zone.…”

Section: Gas Dynamic Disturbance Structurementioning

confidence: 99%

“…Moreover, as seen from figure 3, a relative voltage U > 0. Physically it can be explained by appreciably increasing (E/N ) cr in a heated gas in regions 2, 3 and 4 due to electron attachment to vibrationally excited SF 6 molecules (see [1,10]) at practically unchanged gas densities in combination with greatly increasing gas densities in regions 1 at (E/N ) cr -values approaching (E/N ) T 0 cr . Keeping the aforesaid in mind, we can state that the relationship…”

Section: Gas Dynamic Disturbance Structurementioning

confidence: 99%

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Dynamics of a self-sustained volume discharge in laser-shock-disturbed SF₆-based mixtures

Belevtsev

Firsov

Kazantsev

et al. 2009

J. Phys. D: Appl. Phys.

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This paper reports on first systematic investigations into the dynamics of a self-sustained volume discharge (SSVD) in SF6-based mixtures pre-irradiated by a pulse CO2 laser. Two different illumination geometries are considered, one with a diaphragm slit arranged normal to the central electric field line of the discharge gap and the other with the discharge gap being wholly irradiated. The pattern of a laser-induced gas dynamic disturbance has been theoretically drawn starting from a shock wave theory and visualized by taking SSVD photographs. The delay times between the laser and voltage applications were varied from a few to several tens of microseconds. It has allowed us for the first time to obtain information, based on measuring the discharge voltage, about how long the mixtures considered are capable of being exposed to high temperature with no dissociation. The dynamic barrier effect found in our previous works is thoroughly investigated in both illumination geometries and the observed discharge patterns are qualitatively treated in terms of the electric field distortion by the surface charges at the shock wave fronts. The corresponding surface charge density is numerically estimated. The concept of controlling the electric field distribution over the discharge gap using the dynamic barrier effect is put forward.

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The influence of vibrational excitation on the burning voltage of a pulsed electric discharge in HF laser working media

Cited by 20 publications

References 15 publications

The critical reduced electric fields in SF₆at high gas temperatures

The critical reduced electric fields in SF₆at high gas temperatures

Volume-discharge formed in SF₆and C₂H₆mixtures without preionization

Dynamics of a self-sustained volume discharge in laser-shock-disturbed SF₆-based mixtures

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The influence of vibrational excitation on the burning voltage of a pulsed electric discharge in HF laser working media

Cited by 20 publications

References 15 publications

The critical reduced electric fields in SF6at high gas temperatures

The critical reduced electric fields in SF6at high gas temperatures

Volume-discharge formed in SF6and C2H6mixtures without preionization

Dynamics of a self-sustained volume discharge in laser-shock-disturbed SF6-based mixtures

Contact Info

Product

Resources

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The critical reduced electric fields in SF₆at high gas temperatures

The critical reduced electric fields in SF₆at high gas temperatures

Volume-discharge formed in SF₆and C₂H₆mixtures without preionization

Dynamics of a self-sustained volume discharge in laser-shock-disturbed SF₆-based mixtures