Self-initiated Volume Discharge Research Articles

Self-Organization of Dissipative Structures in Gas-Discharge Plasma of Self-Initiated Volume Discharge

It is shown that the features of the development of the self-initiated volume discharge in gas mixtures of a non-chain electrochemical HF laser are caused by self-organizing processes of dissipative structures representing plasma diffusion channels. The formation features of diffusion channels in the gas-discharge plasma of the self-initiated volume discharge are determined.

Самоорганизация газоразрядной плазмы в SF-=SUB=-6-=/SUB=- и смесях на его основе

It was shown that the dynamics of a self-initiated volume discharge in SF6-based mixtures can be explained on the base of the ecton model of the cathode spots birth and the current density limiting effect due to the gas mixture molecular components dissociation.

Repetitively pulsed non-chain DF laser with pulse repetition frequency up to 50 Hz

The design and performance of a closed cycle repetitively pulsed non-chain DF laser based on self-initiated volume discharge is presented. In order to effectively solve the problem of large volume uniform glow discharge in non-chain pulsed DF laser, a voltage doubling reverse circuit in the Fitch generator was used. The working mechanism and effects of the voltage doubling circuit was analyzed theoretically according to closed loop equation of RLC circuit, and the results were in good agreement with the experiment. The performance of non-chain DF laser operating in both single pulse mode and repetitive mode was researched. A maximum output energy of 3.65 J and a technical efficiency of 3.12% were recorded in single pulse mode. A laser power of 150 W was obtained at the repetition rate of 50 Hz, the amplitude difference of laser pulse was better than + 8%, and the laser pulse width was about 135 ns.

Environmentally friendly HF (DF) lasers

Dedicated to the 100th anniversary of the birth of Academician A M Prokhorov, this paper reviews the physics of self-sustained volume discharge without preionization—self-initiated volume discharge (SIVD)—in the working mixtures of non-chain hydrofluoride HF (deuterofluoride (DF)) lasers. The dynamics of SIVD in discharge gaps with different geometries is thoroughly described. The mechanisms for the restriction of current density in a diffuse channel in electric discharges in SF6 and SF6 based mixtures (which determines whether SIVD is possible) are proposed and analyzed using simple models. The most probable mechanisms are the electron impact dissociation of SF6 and other mixture components, electron–ion recombination and electron attachment to vibrationally excited SF6 molecules. Starting from a comparative analysis of the rate coefficients of these processes, it is shown that electron–ion recombination is capable of compensating for electron detachment from negative ions via electron impact. It is also established that SIVD is not only observed in SF6, but also in other strongly electronegative gases. The factors that determine the uniformity of the active medium in non-chain HF (DF) lasers are analyzed. Some special features of non-chain HF (DF) lasers with different apertures operating are carefully examined. Consideration is given to the problem of increasing the aperture and discharge volume of non-chain HF (DF) lasers. Based on our experimental results, the possibility of increasing the energy of such lasers to ~1 kJ and above is shown.

Diffuse volume-discharges without pre-ionization formed in SF6 and C2H6 mixtures

It has been shown that a volume discharge is forming in non-uniform electric-field rough cathode and even anode without pre-ionization in SF6 and C2H6 mixtures. The discharge is presented with many diffuse channels attached to bright circular cathode spots that diverge towards the anode, with the channels overlapping, form a spatially uniform glow discharge. Self-Initiated Volume Discharge (SIVD) has been performed at a total mixture pressure up to 8 kPa and energy deposition up to 200 J/L. The experimental results indicate that Self-Sustained Volume Discharge (SSVD) in SF6 and C2H6 mixtures develops in the form of SIVD, which is promising for creation of high energy and pulse-periodic HF laser.

High-power self-controlled volume-discharge-based molecular lasers

An investigation is made of the characteristics of the formation of a self-controlled volume discharge for pumping CO2 lasers, i.e., self-sustained volume discharge (SSVD), which involves the preliminary filling of a discharge gap by an electron flux from an auxiliary discharge plasma. It is determined that this method is suitable for large interelectrode gaps, that distortion of the electric field in the gap by the space charge of the electron flux plays an important role in the formation of the discharge, that the electrodes could be profiled dynamically during propagation of an electron flux through the discharge gap, and a SSVD could form in systems with a strongly inhomogeneous field. High-power SSVD-based CO 2 laser systems are created and investigated. Another type of self-controlled volume discharge without preionization, i.e., a self-initiated volume discharge (SIVD), in nonchain HF lasers with SF 6 –C 2 H 6 mixtures is also investigated. It is established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady-state value. As new channels appear, the current that flows through the channels formed earlier decreases. The volume occupied by the SIVD increases when the energy deposited in the plasma increases, and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously when the current increases. The possible mechanisms that explain the observed phenomena, namely the dissociation and electron attachment of SF 6 molecules, are examined. A simple analytical model is developed that makes it possible to describe these mechanisms at a qualitative level. High-power SIVD-based HF(DF) lasers are developed and tested.

High power self-controled volume discharge based molecular lasers

AbstractAn investigation was made of the characteristics of the formation of a selfcontroled volume discharge for the pumping of CO2 lasers, i.e. self-sustained volume discharge (SSVD), which involved a preliminary filling of a discharge gap by an electron flux from an auxiliary-discharge plasma. We have found that this method was suitable for large interelectrode gaps, that distortion of the electric field in the gap by the space charge of the electron flux played an important role in the formation of the discharge and that the electrodes could be profiled dynamically during propagation of an electron flux through the discharge gap and a SSVD could form in systems with a strongly inhomogeneous field. High power SSVD based CO2 laser systems have been created and investigated.Another type of self-controled volume discharge without pre-ionization, i.e. a selfinitiated volume discharge (SIVD), in nonchain HF lasers with SF6−C2H6 mixtures was investigated as well in our review. We have established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady state value. It is shown that, as new channels appear, the current flowing through the channels formed earlier decreases. The volume occupied by the SIVD increases with increase in the energy deposited in the plasma and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously with increase in the current. The possible mechanisms which explain the observed phenomena, namely the dissociation of SF6 molecules and electron attachment SF6 molecules, are examined. A simple analytical model, which makes it possible to describe these mechanisms at a qualitative level, was developed. High power SIVD based HF(DF) lasers have been developed and tested.

Development of a self-initiated volume discharge in nonchain HF lasers

The dynamics of a self-initiated volume discharge (SIVD) is studied in SF6 — C2H6 mixtures, which are used as the working media in nonchain HF lasers, employing discharge gaps of different geometry. The results of investigation are consistent with the previously made assumption that there exist mechanisms which limit the current density of a volume discharge in SF6 and SF6-based mixtures. SIVD simulations were performed taking into account the SF6 dissociation by electron impact, the dissociative electron — ion recombination, the electron detachment from negative ions by electron impact, and the ion — ion recombination. The simulation results are in qualitative agreement with experimental results. The electron — ion recombination and the electron detachment from negative ions were found to cancel each other, to within the accuracy of estimates of the rate constants. The dissociation of SF6 (and other components of the mixture) is most likely responsible for the limitation of the current density in the diffusive discharge channel and for the increase in discharge volume with increasing input energy.

Self-initiated volume discharge in nonchain HF lasers based on SF6—hydrocarbon mixtures

A self-sustained volume discharge without preionisation, i.e. a self-initiated volume discharge (SIVD), in nonchain HF lasers with SF6—C2H6 mixtures was investigated. It was established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady state value. It is shown that, as new channels appear, the current flowing through the channels formed earlier decreases. The volume occupied by the SIVD increases with increase in the energy deposited in the plasma and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously with increase in the current. The possible mechanisms which explain the observed phenomena, namely the dissociation of SF6 molecules and electron attachment SF6 molecules, are examined. A simple analytical model, which makes it possible to describe these mechanisms at a qualitative level, was developed.