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Laboratory of Laser Discharges

The Laboratory of Laser Discharges was founded as a scientific unit of the Institute for Problems in Mechanics RAS more than 25 years ago. Primarily the laboratory staff was based on the group of researchers leaded by professor N.A.Generalov, RAS associate member. The group since 1970 deal with plasma physics and mechanics, high-power gas discharge lasers and optical discharges (or laser plasmas). Now the staff of the Laboratory consists of: 9 scientific researchers (2 D.Sc. and 3 Ph.D. among them), 7 engineers and 3 technicians.

Main scientific activities of the laboratory lay in the field of experimental and theoretical studies of various types of gas discharges, including discharges in a fast gas flow. Basic studies in this field stimulate in turn the development of the prototypes of high-power industrial CO2 lasers with high beam quality. The lasers developed and built in the laboratory are then used in experimental tests of the effect of intense laser radiation on different materials and substances. Technological results of the scientific investigations are also the developments of high-power industrial lasers, laser processing machines and laser treatment technologies for industry.

Mikhail Yakimov, Senior Researcher, and Nikolai Solov'ev, Head of the Laboratory, show experimental set-up for studies of a continuous optical discharge to Professor Vladimir E. Fortov and Professor Yury P. Raizer.

Main research activities

1. Continuous optical discharge (COD), or laser sustained plasma. The phenomenon of COD had being theoretically predicted by Professor Yury P. Raizer (IPMech RAS) and was obtained in practice for the first time in the world by the researchers of the Laboratory of Laser Discharges in 1970. COD plasma is sustained due to absorption of laser radiation provided the radiation intensity excided some threshold value depending on laser radiation wavelength, sort and pressure of the gas or gas composition, and may be varied from tens kilowatts to tens megawatts or more per square centimeter.

Continuous optical discharge in the laboratory air sustained by high power CO2 laser beam.

COD plasma stability in the gas flow, as well as radiation characteristics of COD plasma and laser beam refraction in plasma are under close investigation now in the Laboratory. Various aspects of plasma interaction with a forced gas flow and related possibilities of plasma structure, temperature, and stability control are studied in connection with the question of laser radiation transport in a dense plasma. Scientific basis of COD applications for solving different problems in high temperature gas dynamics and applied physics is being developed on the base of these studies.

COD is particularly applied for simulation of solar irradiation at the top of the atmosphere in the experimental stand for outer space conditions simulation for the tests of the materials and devices under high vacuum, extremely high thermal gradients and intense visible, UV and VUV radiation.

Promising COD applications are also studied such as high brilliance wide spectrum light source, or plasma generator for high enthalpy gas flow or high energy neutral particles beam formation.

Experimental stand of the outer space conditions simulation with continuous optical discharge used as radiation source. Additionally the possibility of COD application for stabilization of other discharge types is studied to increase the efficiency of energy transformation in plasma generators.

2. Nonself-sustained glow discharge with ionization by periodic-pulsed capacitively coupled discharge. This new combined glow discharge technology has being developed and first realized in the Laboratory of Laser Discharges. In this type of a combined discharge functions of electric power pumping and ionization are shared between to different sources. This type of the discharge is characterized by high homogeneity and stability in a wide pressure range, and so can provide uniform highly non-equilibrium plasma in tens liters of the discharge volume. The combined discharge technique is used in the laboratory in the studies of mechanics and physics of non-equilibrium plasma, as well as for developing and building high-power gas discharge lasers with high beam quality. This type of combined discharge may be also used in plasmachemical reactors of high productivity.

Self-sustained and nonself-sustained glow discharges in the tube with coaxial gas flow.

High-power fast-transverse-flow industrial laser prototypes "Lantan-2" and "Lantan-3" of up to 5 kW CW or pulsed output power have being developed and built in the laboratory and then were commercially produced. Now experimental prototype of the industrial fast-axial-flow laser up to 4 kW CW or pulsed output power with high beam quality is developed. All the lasers developed realize the technology of nonself-sustained glow discharge combined with capacitively coupled periodic-pulsed discharge, which brings a set of competitive advantages to the laser processing equipment designed on this base.

Laser processing machine with industrial laser "Lantan-3" with nonself-sustained glow discharge combined with capacitively coupled periodic-pulsed discharge ionization.

3. RF-discharge. Experimental studies of various forms of RF-discharge glow had being carried out. The possibilities of application of capacitive RF discharge for gas lasers excitation were also investigated.

Self-organizing phenomena in a capacitive RF-discharge between two metal disc electrodes in xenon.

4. Interaction between turbulent gas flow and glow discharge. It is well known that turbulization of the gas flow may increase the stability of the glow discharge. It was experimentally found and confirmed theoretically in the Laboratory that there is also return effect of the glow discharge on the turbulent flow parameters, particularly on the amplitude and width of the peaks in turbulent pulsation spectrum. A study of the effect of restructuring of the gas flow in the near-field turbulent wake after two cylinders under the influence of the glow discharge. Phenomenological model is proposed to obtain comprehensive description of the effect. Numerical calculation approach to the problem is also being developed.

5. Plasmachemical effects in glow discharges. Composition changes in the laser gas mixtures due to plasmachemical reactions in DC and periodic-pulsed glow discharges were investigated experimentally both in steady state gas and under forced gas flow conditions. Methods of high-power CO2 laser working gas mixture composition stabilization were developed as on the base of specific combined discharge properties, particularly properties of capacitively coupled periodic-pulsed discharge, as well as on the base of the use of low temperature heterogeneous catalysts. Cooperative project with FGUP "NPP ISTOK" is in progress on the use of the catalyst developed in the Laboratory for the improvement of industrial lasers ILGN-802.

6. Promising methods of ozone production. Innovative method of ozone production by mixing supersonic air flow with partially dissociated oxygen coming from plasmatron was proposed and verified experimentally in the Laboratory. Plasmadynamical ozone generator like that exceeds now existing methods 500-700 times in volume productivity with specific power consumption 2-2,5 times lower. This method is likely to find its application in powerful water-treatment systems at large water purification plants of big cities.

7. High-power gas laser resonator developments. Based on the studies of the optical characteristics of high power large volume glow discharges, laser resonators for optimal high quality laser beam extraction were developed and applied to lasers of up to 10 kW CW or periodic-pulsed output power for scientific and technological use. Methods of theoretical and numerical evaluation of different resonator performance taking in account gas dynamics and other specific features of fast flowing gas lasers were developed and tested. Unstable resonators with radially variable output mirror (VRM) reflectivity, different multiple pass folded stable resonators, particularly optimized for fast transverse gas flow conditions, resonators with thermal lens effects compensation by means of cylindrical mirrors were designed and built. Close attention were also paid to output beam polarization systems and external systems of laser beam conditioning.

Optical system elements of high-power fast-axial-flow CO2 laser.

8. Development of automated systems for experiments and laser processing equipment control. Multiple function computer data acquisition and processing systems were developed and used for measurements in experimental studies. Investigation of the properties of high-power CO2 laser as а control object is being carrying out aimed at the development of the optimal control algorithms and further improvement of the control systems of the equipment designed on the base of nonself-sustained high-power discharge technology. Microprocessor automated control systems for industrial lasers "Lantan-3" and "Lantan-3M" were developed and commercialized in the Laboratory.

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