A new-dimensional self-consistent numerical model of vibrationally nonequilibrium gas flow in glow discharge positive column has been constructed. The influence of volume recombination, pre-ionization effect, discharge region length and gas flow velocity on the CO₂ laser active medium gain has been investigated. The results of numerical calculations made a good agreement with the results of IR luminescence diagnostics of CO₂ laser active medium with transverse pumping.

The analysis has been performed of main sources of wave front aberrations in industrial CO₂ lasers, which have an effect upon beam quality. Nonlinear optical inhomogeneities caused by thermal self-action have been studied.

It has been shown that the effect of kinetic heating causes a reduction of thermal stability of gaseous CO₂ laser both self-sustained and non-self-sustained glow discharges. Under certain conditions, growing of initial density fluctuations with time may become possible due to this phenomenon.

The scaling laws for designing high power CW CO₂ lasers have been established, considering the saturation intensity, optical damage threshold of the optical resonator components and the small signal gain. In transverse flow CO₂ lasers having discharge of square cross section, the discharge length L and its width W for a specific laser power P (Watt) and gas flow velocity V (cm/s) can be given by L = 1.4 x 10^{4/P(superscript ½}V^-1 cms and V = 0.04P^½cms. The optimum transmitivity of the output coupler is found to be almost constant (about 60%) independent of the small signal gain and laser power. In fast axial flow CO₂ lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also discussed.

This review paper presents in summarized form the results of a thorough basic research on EDMG physics and applications to gas-flow discharge lasers, as well as an analysis of the world state of the art in this field. The fundamental physical idea of the paper is based on a conclusion that the CW EDMG is a new form of gas discharge, different from the classical glow discharge. The CW EDMG plasma is inhomogeneous in the current direction; in many cases it is substantially unstable. The paper contains a survey of experimental data, analytical models and numerical analysis of the EDMG. It gives a possibility of estimating the main electrical and power input properties of fast-flow gas discharge lasers. One of the most important physical and practical achievements of the R&D is a possibility of dramatic increase (up to atmospheric range) of EDMG working pressure. The paper might be of interest to physicists and engineers in the fields of laser and electrical discharge techniques, as well as for ecological and plasma-chemical applications.

The general features of the electron beam sustained lasers and some peculiarities of their operation are described. The processes that determine plasma conductivity and energy balance in plasma are considered. The spectrum of laser radiation and divergence of laser beam are given.

A calculation model of maximal current of the transversal self-sustained gas discharge has been built taking into account the gas state in the discharge positive column and in cathode areas. An effect of laminar and turbulent modes of gas flow and channel sizes on the discharge maximal current has been considered.

Process in volume discharge initiated by positive corona are considered.

The outcomes of spectroscopical investigations of RF-discharge plasma parameters are represented for the CO₂ laser mixtures. The main emphasis is made on the exploration of spatial instabilities of luminescence intensity and gas temperature distribution in such discharge. Unlike the theoretical prediction it is shown that sizes of the sheath in a RF discharge weakly depend on excitation frequency and gas pressure.

Using a mass-spectrometer investigations for gas composition of active medium of waveguide RF-excited CO₂ lasers operating in the sealed- off mode h ave been conducted. It has been stated that degrees of CO₂ dissociation comprise 10-67% depending on wall material of a discharge bore and depend little on conditions of discharge excitation. Low CO₂ dissociation degrees have been achieved when using a gold catalyst in laser discharge volume.

By the present time RF-excited waveguide CO₂ lasers have become widely spread and are applied in various fields of science and technology. High specific energy characteristics, small size and resistance to climatic and mechanic effects, possibility of continuous tuning of the emission frequency make their use in infra-optical communication and location systems, in systems of remote control of environmental pollution and in precision measuring systems highly promising. The above applications put high demands to spatial characteristics of the emission of waveguide CO₂) lasers; they require radiation pattern axis stability, uniformity and stability of field distribution over the cross sections of the beam both in the near and far zones. Besides appearance of additional spectral components in the range of emission frequencies is unacceptable in systems using heterdyne information processing. However, in some experimental works and in attempts to introduce these devices into actually operating apparatus some cases of deformation of spatial characteristics of radiation from sample to sample were notd in the course of operation, as well as the so-called whistle of transverse modes even with visually uniform transverse distribution in the radiation spot. In the light of the above there is continuous attention and interest to investigation of spatial and time response of the emission spectrum of RF-excited waveguide CO₂ lasers.

Nowadays, the compact reliable multi-channel CO₂ lasers have been developed which are intended for tackling technological problems of material processing. Among them are the JIH01.2HM, JIH-3.5HM lasers and the systems of even higher power. The paper presents the out comes of studying the spectral composition of multi-channel CO₂ lasers, the results of evaluation of gas temperature active medium gain by radiation proper spectrum. The investigations are aimed at radiation power build- up, output characteristics improvement through the use of regeneration systems. The paper is also concerned with generation spectrum dependence on resonator length, output mirror reflectance, active medium pressure and composition, energy input.

Ionization instability of the discharge on the small-scale nonuniformities of gas density was investigated. It was shown that high- intensity laser radiation reduces the threshold of gas discharge ionization instability in the fast-axial-flow (FAF) laser. The turbulent characteristics of gas flow in the active medium of the gas-discharge laser were measured experimentally by luminescence method and an estimation of their influence on the wavefront distortion of the laser beam has been made.

The properties of output beams for slab CO₂ lasers of output power in the range from few tens of watts up to 1 kW with waveguide-unstable cavities have been studied both theoretically and experimentally. It is shown that such lasers provide close to single-mode operation, smoothing-out one-peak profile and near-diffraction-limited beams at high specific output power. New slab cavity scheme with phase shifting array mirror has been proposed and developed. A highly spatially suppressed and highly bright output beam was obtained.

The intermediate power compact continuous wave (CW) CO₂ waveguide (WG) lasers have been studied and developed. Most attention is devoted to small-bore slab WG devices. The results of studies of space discharge electric and laser parameters, effects of pumping frequency, electrical matching of RF supply and laser head load as well as cavity optimization are briefly described and taken into account in practical design. Two models of slab lasers are described and compared with some other known models.

Development of a parametrical line of lasers on carbon dioxide (LCD) for wide application range, based on similar constructional and technological solutions, is reported.

Experimental and theoretical investigations were made of the power and beam shape by waveguide CO₂ laser with slab geometry and RF excitation of the active medium with waveguide-unstable cavity. The output power in CW mode was 54 W without astigmatism quality beam when external correcting optics was not used.

Experimental, engineering and modeling aspects of development of high- power industrial waveguide single-beam CO₂ lasers are considered. Parameters of an experimental model of this type laser with 0.5 kW beam power are presented and relevant critical problems are discussed. Beam output characteristics depending on different parameters are offered.

Strict requirements of modern industry and medicine to laser beam quality, stimulated to fulfil a lot of special researches have been undertaken concerning: a) gas discharge stability and uniformity; b) enhancement of active medium optical nonuniformities in the presence of laser generation; c) new concepts of optical resonators; beam power modulation with a controllable coupling mirror. As the result of these investigations, several series of fast-flow and of diffusion-cooled waveguide industrial CO₂ lasers in 0.5 to 10.0 kW beam power range have been designed in the IPLIT RAN.

The multifunctional laser LOK-3MF has been developed on the basis of the CW laser with DC pumping and cross gas flow¹. An optical resonator of the laser has been developed on the SFUR (Self Filtering Unstable Resonator) scheme². High beam quality is provided by this scheme (full angle divergence is 0.7 mrad on 0.86 power level at beam diameter 30 mm). The laser generates 3 kW output power without any additional equipment. Besides, it is equipped by four accessory units in a feedback arm to provide a variety of operating modes. 1. Single-frequency CW mode with capability of monotone line tuning in bands of 9.4 micrometers and 10.4 micrometers (about 70 lines in all) with maximum output power up to 2.6 kW at line 10P20 and per-unit frequency instability of the order of 10^-7. As it as been shown, there is a possibility to reduce a laser line width down to 50 kHz. 2. The mode with simultaneous two-wavelength lasing at 40 pairs of adjacent laser lines with maximum total power up to 2.5 kW. A simultaneous generation of 3 adjacent lines have been observed in 9R branch. 3. A mode with rapid tuning of the generation line (with about 1 microsecond(s) transition time) in combination with an opportunity to form any given spectral-temporal sequence. The generation spectrum and output power are the same, as in mode 1. 4. Repetition-rate Q-switching mode with high peak power (up to 800 kW) and the average one (up to 2.8 kW) with pulse repetition rate control in the range of 1-100 kHz. 5. The repetition-rate Q-switching mode in combination with line-tuning (such as in mode 1) has been developed for selective photochemistry and laser isotope separation. A selection of applications of the laser for material processing and for producing of a new variety of gas discharge - powerful optical pulsating discharge are presented.

The parameters of a repetitive-pulse CO₂ laser are given and its construction is described. The energy characteristics of the radiation and the shape of the laser pulse have been investigated as a function of the composition and pressure of the mixture. The aspects of the design approaches are considered: the implementation of rotation in vacuum by means of magnetic clutches, the presence of two discharge chambers, and the automatic control elements. The functional capabilities eligibility, and lifetime of individual elements and assemblies are evaluated.

Utilization of the working gas regeneration system by high-power multibeam CO₂ lasers with diffusion cooling featuring higher consumption of working gases will allow to lower costs for their operation and to improve the ecological situation. This article considers the matter of applying heat regenerators. Evaluated hereby are contents of possible impurities at the unit gas-vacuum circuit and working gas degradation degrees. Concentrations of nitrogen oxides and CO for multibeam lasers were measured in the process of operating the laser. Measurements of amplification factor have been carried out.

Variable reflectivity output mirros (VRM) provide a good possibility for output coupling of diffraction limited beams both from gas and solid state laser media. A set of VRM resonators was designed and tested in fast-transverse-flow CO₂ laser. It was shown that the phase profile of the output beam in VRM resonator may be improved by the appropriate design of the VRM output coupler. The results of experimental and theoretical studies of unstable VRM resonators operation in CW CO₂ lasers with output power up to 3 kW are presented. It was shown that beam generated in VRM unstable resonator may be characterized correctly in terms of M² and K factors.

Controllable base Fabry-Perot interferometer (FPI) was used as the output mirror of CW CO₂ laser to provide the pulse-periodical generation mode. Frequency range 0-5 kHz and pulse length range 0.1-10 ms with 100% modulation depth were obtained. The FPI-based method of power control and stabilization was realized.

Radially polarized radiation 1.8 kW was first obtained in an industrial high-power CO₂ laser. Special reflective elements with axial polarization selectivity 22% were used as rear mirror in the laser. The output radiation consisted mainly of an unpolarized mode TEM₀₀ and a radially polarized mode R-TEM₀₁. The maximum degree of polarization of the beam measured in the far and near field was about 80% and 90% correspondingly.

Optical and spectroscopic methods were used in studying near-surface plasma that is formed under the effect CW CO₂ laser of (2- 5)x10⁶W/cm² power density upon stainless steel in He and Ar shielding gases. The variation of plume spatial structure with time has been studied, the outflow of gas-vapor jets from the interaction area has been characterized. The spectra of plasma plume pulsations have been obtained for the frequency range Δf = 0-1 MHz. The temperature and electron concentration of plasma plume have been found under radiation effect upon the target of stainless steel. Consideration has been given to the most probable mechanisms of CW laser radiation-metal non-stationary interaction.

Using various methods of investigation (mathematical modeling, modeling of processes of auxiliary gas outflow using physical models simulating the real ones, visualization of real processes of laser cutting), the influence of the geometry of the system the nozzle - the obstacle and of the nozzle on the power and hydrodynamic parameters of the auxiliary gas jet is shown. The role of gas on the precision and the surface finish of precise contour workpieces of sheet metal is revealed. Using models geometrically simulating the real ones, the structure and the form of the gas jet at the same time of its outflow from the nozzle and the slot are shown. The dimensions of the inlet of the nozzle (d₀) and the distance to the obstacle ((Delta) h), at which the gas jet shows the maximum effect of penetration into the slot, are determined.

According to one of today's most accepted visualizations of the first viable realizations of The Computer Integrated Manufacturing Plant, C.I.M.P., the manufacturing systems herein discussed tend to be multiprocessing, and tend to incorporate the lasers to take advantage of the unique capacities of the laser as a processing tool. Finally also the present laser sources, while having been for a long time more than sufficient, inevitably tend also to new generations. Said visualizations stand in the belief that the first realizations of the C I M P most likely will use flexible multiprocessing machines, which, for flexibility requirements, grow in multi-station cells, in their aggregation in isles and finally in complete manufacturing centers. To constitute the CIMP all partaking elements must be the most easily amenable to Computer Aided Design, CAD, and Computer Aided Manufacturing, CAM. Another basic requirement is that all elements constituting the CIMP must possess the highest System Efficiency and Energy Efficiency at the level of the single element and of its aggregations throughout the various combinations at each and every operating level of said aggregations, up to that of the CIMP. The mastering of the CIMP design constitute a New Discipline that presents very formidable but necessary tasks. Of these the first examples were those related to the early flexible manufacturing system Design Programs. For what concerns the laser processing machines and their integration in manufacturing systems, attention must be given to not repeat the events that hindered their diffusion in the production field keeping it at a level much lower than the expectations and their true potential. Said events stemmed from the confusion between System Efficiency and Energy Efficiency, which persisted for too long and is still common. This has taken place at the levels of introduction of a single element into the combination of the several elements constituting a linear arrangement such as a Transfer Production Line. It because greater and with graver consequences in the case of arrangements possessing more than one degree of product routings, arrangements, as previously mentioned, which evolved in the Flexible Manufacturing Centers.

The current level of laser technology development and understanding of the process of laser radiation interaction with materials, attained by the world laser research community, including the scientists from Russian and from the IPLIT RAN, particularly, provides new possibilities of updating the technology of materials processing and diagnostics in machine-building and metallurgy. Several institutes of Russia, primarily the IPLIT RAN, develop and produce practically all basic types of industrial lasers used in materials processing. These lasers provide a basis for development and application of welding, cutting and surface treatment. Alongside with the above-listed traditional technologies of laser materials processing (LMP), a progress has been made in development of a new and promising laser-computer technology of 3D parts rapid prototyping. Besides, the laser-computer methods of non-contact diagnostics of subsurface defects and stressed states are of great interest to machine-building and metallurgy.

It is known that comparatively small beam divergence and sufficiently high beam intensity of CO₂ lasers give possibility of their application in various technological processes, that demand distant interaction. The results of some technological applications of continuous wave (CW) and high repetition rate (HRR) CO₂ lasers with average power up to 50 kW are presented. It is shown that these lasers can be used in the field of nuclear power.

Decommissioning of nuclear reactors using laser remote dismounting and welding was experimentally proved at a nuclear reactor of Kursk Nuclear Power Plant. The main reason of laser beam application in this case is the marked decrease of radioactive exposure of the service personnel. The use of a high-power laser beam provided for laser cutting and welding processes realization at a distance up to 35 m between the laser and the workstation placed behind a radiation shield. By application of laser cutting gas and dust contamination is ten-fold decreased. Some results of decommissioning application of a stationary laser workstation based upon a 5 kW fast-transverse-flow discharge CW CO₂ laser TL-5M installed at a nuclear reactor site are presented. A special high-beam- quality model of the laser was developed to satisfy the needs of decommissioning. Laser cutting process was applied to decommissioning of fuel channels (FC) of RBMK-1000 reactor, after their extractor from the reactor active zone during the procedure of channels replacement.

The high power mobile laser technological complexes with output power 5 kW (MLTC-5) and 50 kW (MLTC-50) have been developed and experimentally tested. Various perspective areas of industrial applications of mobile laser technological complexes are considered. The results of some technological experiments are given.

The paper deals with laser technological units (LTU) based on multi-beam lasers of 1 to 10 kW power. To save working gases the laser technological units employ regeneration systems. The LTU have been the basic units used in multipurpose systems for laser processing various parts of the kind of rotation bodies or plane parts, cranckshafts, etc., as well as in special-purpose systems and automatic lines with the full cycle of auxiliary technological operations which are necessary to perform laser processing. The technologies of heat treatment of parts with the use of multi-beam lasers have been developed for the purposes of improvement of heavy-loaded rubbing parts wear resistance; local treatment of non-rigid parts; reduction of labor consumption in some cases of thermo-chemical treatment or induction (bulk) hardening replacement with laser irradiation; reconditioning of worn parts by precision facing, alloying or similar processes.

The paper studies the influence of CO₂ laser continuous-wave radiation on domain structure of grains of anisotropic electrical-sheet steel having ideal Goss orientation. Fragmentation of 180$DEG domains under laser beam action has been experimentally revealed. It has been shown that high-speed processing of the surface of anisotropic electrical-sheet steel with continuous-wave laser radiation makes it possible to improve the domain structure and to reduce the losses by magnetic reversal P_17/50 without substantial lowering of magnetic induction B100. To carry out the technological process, an automated laser technological system (ALTS) has been developed and produced for processing iron circuit plates of 400x1200 mm size with speeds up to 100 m/s.

The possibilities of material surface processing by different types of lasers (continuous-wave, high repetition rate CO₂) with the aim of corrosion resistance growth are discussed. The researches of structural peculiarities and mechanisms of corrosion behavior improvement of metal materials in hostile environments after laser welding, melting and alloying, and the examples of industrial applications are presented.

Since the advent of lasers, these unique sources of highly intense and monochromatic radiation have been proposed as excellent tools to induce or catalyze chemical reactions. Due to the great interest to the problem of isotope production, investigation and application, the laser method of isotope separation has received the most attention worldwide and may be the first major commercial application of lasers to chemistry. Laser methods of isotope separation are based on high selectivity and power of laser sources of radiation. One of the most prominent method is based on the effect is isotope-selective multiphoton dissociation of molecules by IR-radiation (MLIS-method). This phenomena was discovered in Russia in 1974 and developed from scientific investigations to industrial scale production of ¹³C isotopes in collaboration between the Kurchatov Institute of Atomic Energy, TRINITI and Institute of Spectroscopy of RAS. Demonstration facilities for sulfur and carbon isotope separation with average productivity up to 2 g/h have been created as a result of collaboration and these systems are aimed at optimization of MLIS process and evaluation of its cost efficiency. Experiments show that laser produced isotopes are far cheaper as compared to any conventional technique. Results of basic scientific research, existing technological cooperation allow to start building a laser isotope separation plant. Light element isotopes produced there can answer a wide variety of demands in many technologies. These isotopes can be readily used in medicine, agriculture, environmental monitoring, etc.