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The possibility of controlling the development rate of the incomplete staged of the discharge sliding over a solid dielectric surface is experimentally shown. Depending on the gas pressure and power supply voltage, the development rate of the incomplete stage of the discharge in air sliding over the solid dielectric surface is determined. It is shown that the discharge development rate varies from 1.4 × 106 to 7.8 × 106 cm/s in the pressure range from 10 to 60 Torr voltage from 4 to 12 kV. Emission of the second positive system of nitrogen dominates in the emission spectrum of the incomplete sliding discharge.

This paper presents an analysis on the possibilities of controlling the radiation pattern of Yagi-type multielement plasma vibrator antennas. The plasma vibrator antenna in its operating band is shown as a narrow-band filter. In a multielement linear plasma vibrator antenna, turning off a passive plasma vibrator makes it possible to control the beam width electronically.

Conditions for gas ionization in the field of a slow surface wave excited by a microwave source are considered. The gas ionization rate and the plasma density distribution over the radius of the discharge tube were studied by the optical method. The experiments were conducted in a dielectric tube with a radius much smaller than the tube length, the gas pressure being ~1–3 Torr. It is shown that the stationary distribution of the plasma density is determined by diffusion processes.

Characteristics of the plasma layer (a plasma antenna of dipole type), excited by the radiation of a transmitter such as the carrier density distribution over the radius of the dielectric tube (near the boundary) and the growth rate of the plasma region along the tube length are considered. It is shown that it is possible to distinguish such typical dimensions as the radius of the dielectric tube, the radius of the plasma column, and the thickness of the skin layer, and, depending on relationships between these dimensions, consider the influence of the transition layer on excitation of the surface wave in the plane or cylindrical symmetry.

A reflector plasma array antenna is investigated. A plasma array with a controlled pattern is created with the help of a discharge creeping over a dielectric surface. The scattering microwave radiation pattern is calculated for the vertical and horizontal polarizations of the radiation incident on the plasma array.

Lasers, sources of coherent UV and vacuum UV radiation, plasmachemical reactors, reactors for cleaning fouled gases, etc., can be classified as devices the working medium of which is plasma formed as a result of the interaction of a high-current relativistic electronic beam with gas. Efficiency of such devices which are united under the common name “systems of injection gas electronics” (SIGE) depends mainly on the efficiency of energy transfer from a beam to gas (ηg = Wg/Wb) and that of the transform of the energy transferred to gas into the energy of the ultimate product Win (ηin = Win/Wg). As a special case of SIGE, an experimental bench laser is considered. The new efficient method of pumping is supposed to be implemented on this laser to optimize the energy contribution ηg and useful output ηin.

Fluorescence spectra induced by a He-Ne laser in a complex biological medium (blood plasma) are studied. The statistical analysis of the spectra reveals regular correlations between the spectral parameters and concentration of substances known as porphyrinic pigments. The common factors of the spectral characteristics of fluorescence spectra are chosen as the diagnostic parameters. A model for differential diagnostics based on factor analysis is proposed.

The infrared transmittance spectra and dark conductivity of wafers fabricated from nanocrystalline silicon powder (nc-Si) have been studied. The initial nc-Si powder is first synthesized by laser-induced silane dissociation, with the temperature of the surrounding buffer gas varied from 20 to 250°C, and then compacted at pressures from 108 to 109 Pa. It is found that compaction of the nc-Si powder results in formation of Si-H, Si-CHx, and Oy-Si-Hx structures (x, y=1–3). The formed structures break down under annealing, with the Si-H and Si-CHx complexes disintegrating at the lowest annealing temperature (t = 160°C). The dark conductivityof the nc-Si wafers is shown to increase along with the buffer gas temperature at which the starting powder was prepared. Two temperature regions are found in which the dark conductivity behaves in radically different ways. At wafer temperatures T ≥ 270 K, conductivity is mediated by free carriers, whereas, at lower temperatures, electron transport is governed by hopping conduction over localized states in the band gap.

A mathematical model describing the form of the surface of propagating wave energy is suggested.

Ultrafine powders with a mean particle diameter (20–30) nm were synthesized from high purity SiH 4 by laser-induced gas phase reactions and studied by transmission electron microscopy. Results showed that the powders consisted of Si crystals with an amorphous shell, or spherical Si crystals without the shell. Twinning of crystals often took place. Both types of crystals: poly and mono were observed inside an amorphous shell. The mechanism of the formation of all types of nanoparticles is proposed.

The development of a high-voltage discharge above the water surface is considered. The peculiarity of the observed type of discharge is explained by the process of water evaporation.

The experimental results on breakdown characteristics of a discharge gap containing water vapor are presented. The results obtained show that the breakdown voltage between metal electrodes placed above water and when one electrode is immersed in water significantly increases at a saturated vapor temperature of 90°C and above. This effect can be an explanation of the features of the electric discharge development above the water surface.

This review paper presents the results obtained during the development and study of three high-power wide-aperture CO 2 lasers (λ=10.6 μm) pumped with a discharge controlled by an electron beam. In developing these lasers, the method of formation of a space discharge at elevated pressures due to uniform ionization of the working mixture by an electron beam with an energy of some hundreds of kiloelectron-volts was used, which was proposed by researchers at the Instute of High-Current Electronics (IHCE).

The method of spectroscopy with temporal and spatial resolution was used in an investigation of the collision, with a ring-shaped obstacle, of a plasma created by interaction of laser radiation with a solid target. This collision excited autoionizing states of C II and C III ions. The velocities of ions with diiferent ionization multiplicities, as well as the electron density ne and the electron temperature Te were determined by an expanding plasma flux, and the density and temperature were also found for the case when the plasma collided with the obstacle. The kinetics of excitation of autoionizing states was determined when the pressure of a buffer gas in the vacuum chamber was varied. The spatial distributions of ne and Te were used to analyze the mechanism of excitation of the autoionizing states.

A pulsed TEA CO2 laser was used in an investigation of the influence of the pump radiation parameters (mode composition, wavelength, pulse duration), of the focusing conditions, of the properties of the material (absorption coefficient), and of the operating conditions (temperature) on the efficiency of conversion to the second harmonic and on the angular dependences of phase matching in ZnGeP2 crystals. The calculated results were found to be in good agreement with the experimental data.

The authors have improved a procedure for preoperatively preparing patients with progressive drug-resistant fibrocavernous tuberculosis. This has been achieved by using ultraviolet laser irradiation (wavelength 248 nm) of the cavity walls in the multimodality treatment of this disease. Endocavitary laser irradiation increases preoperative preparation and surgical treatment and reduces the number of postoperative complications.

The wafers of thickness 60μm÷100μm were made at compression of nanocrystalline silicon (nc-Si) powders in a range of pressures from 108 up to 109 Pa. Optical and electrical properties ofthese wafers have been investigated by means of registration of IR transmission spectra and dark conductivities. Analysis of IR absorption spectra of wafers shows that structures Si-H, Si-CHx and Ox-Si-Hy (x,y=1÷3) are formed at a pressing of nc-Si powder. We believe that these structures are formed at pressing of powder after break of links in network of a silicon atoms and consequent saturation of Si-dangling bonds by hydrogen, carbon or oxygen atoms which are located on free surfaces of silicon particles. It is found that dark conductivity of a wafer is depending on temperature of buffer gas in which original powder is formed. Wafers which have been made of the powders created at higher temperatures of a buffer gas flow had more pronounced hydrogen microstructure and higher dark conductivity. Analysis of dark conductivity vs. temperature T of the wafer shows that at the temperatures higher than approximately 270K the conductivity follows Arrhenius behavior with single activation energy, and at lower ones, conductivity is depending on T as: σ=(A/T1/2)-exp(-B/T1/4). Last equation allows asserting that variable-range hopping is mechanism oftransport in nc-Si wafers at temperatures T

A new method is proposed for investiging the behavior of the nucleus of a living cell with damage to different parts. A laser set-up based on a projection microscope with image time scan has been designed. A new type of N2-laser is used as an external source of the affecting radiation. The construction allows one to irradiate a biological object with the radiation from a copper laser which forms the base of the projection microscope.

The found bactericidal activity of ozone and oxygen mixture containing ozone, 10 mg/l, and ozoned solutions of furacilin (dilution 1:5000) and chlorohexidine (0.05%) against the nonspecific microflora and Mycobacteria tuberculosis allowed them to be used in the treatment of 55 patients with pleural empyema. Analyzing the outcomes of treatment in these patients versus 59 matched patients indicated that local ozone therapy accelerated sanitation and stimulation of reparative processes in this disease on the average by a fortnight. Local ozone therapy used in the preoperative preparation of patients with pulmonary tuberculosis and pleural empyema reduced the number of purulent postoperative complication to 17.7% versus 30.4% in the controls, enhanced the efficiency of multimodality treatment by 15.6% and reduced mortality by 9.5%. Analyzing the results of prevention of purulent bronchopleural complications after pleuropulmonectomy in 31 patients in the experimental group and in 35 in the control one showed that with local ozone therapy, complications occurred in 16.1 and 28.6%, respectively, and the efficiency of surgical management increased by 13.1% and mortality rates reduced by 9.6%.

Silicon nanopowders produced by CO2-laser-induced decomposition of SiH4 in a flow reactor have been investigated. The particles of these powders can be described as polycrystalline silicon grains surrounded by a Si-amorphous shells.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A study was made of the problems of using BaxSr1–xNb2O6 (BSN) crystals to measure high-power CO2 laser radiation of λ = 10.6 μ wavelength. An experimental investigation of BSN crystals with x = 0.25 yielded the characteristics of a pyroelectric detector of this type: responsivity 20 V/MW; response time 2 nsec; linear up to 3 MW/cm2; optical strength up to 9 MW/cm2. Pyroelectric detectors based on BSN crystals were used to detect and analyze the spatial and temporal structure of short high-power CO2 laser pulses.

The paper is concerned with the problems of application and operation of BaxSr1−xNb2O6 (BSN) crystals as detectors of powerful short pulses of radiation from a CO2-laser with λ = 10.6 μm. The thermodynamic and optical characteristics of BSN crystals with a composition X = 0.5 are presented. The dependences of permittivities e′ and e″ and tgδ of the frequencies up to 400 MHz are measured. Thermodynamic analysis of the detector operation is made by solving a one-dimensional equation of heat conduction from a source of internal heat distributed by the Bouguer law. These crystals were used for experimental investigation of recording powerful radiation pulses. The BSN crystals are shown to have a voltage responsivity of 20 V/MW, time rise—2 ns, linearity—up to 3 MW/cm2, strength—up to 9 MW/cm2. A design of the pyroelectric detector is presented. The detector is applied for investigating the time and spatial structure of the powerful short pulses from a CO2-laser.

An investigation was made of the near-ultraviolet part of the spectrum of radiation from a plasma created by irradiating a solid target in a low-pressure gas (0.5–15 Torr) with CO2 laser radiation of intensity up to 0.1 TW/cm2. During excitation of a buffer gas by a shock wave, spatially selective emission of individual spectral lines with excitation energies of 35–60 eV was observed. The radiation formed a hemispherical halo of radius which was a function of the intensity of the laser heating radiation and of the buffer gas pressure. The halo was due to spatial localization of the ions with the highest charge multiplicity generated in a shock wave excited in the gas near the target heated by laser radiation.

The method of double-exposure holographic interferometry was used to investigate the gasdynamic collapse of a laser plasma initiated by a gigawatt CO2 laser pulse. The laser beam was tubular and it was focused onto a carbon target. The holographic method enabled the parameters of the laser plasma to be measured with a spatial resolution of better than 25 μ. The spatial distribution of the electron density during the laser pulse interaction was determined. Estimates were obtained of the axial and radial velocities of the erosion laser plasma and an analysis was made of the relationship of these parameters to the experimentally determined shock wave velocity in the residual gas. It is proposed to use the laser plasma formed during a gasdynamic collapse as the active medium of short-wavelength lasers.

Results are presented of a comparative study of the radiation spectra of spark and surface discharges in the 114–200 nm range. It is shown that both complete and incomplete surface discharges are a more efficient source of ultraviolet radiation for preionization of the active volume of CO2 lasers than spark discharges. This is attributed to the possibility of concentrating the radiation energy in the required spectral range and of locating the discharge plasma in the optimal position with respect to the laser active volume. An analysis of the time behavior of the radiation intensity of the most characteristic spectral lines showed that the changes in the spectrum of an incomplete surface discharge with polarity reversal of the supply pulse were associated with the surface-discharge-formation mechanism.

The dependence of the minimum initial electron density necessary to form a volumetric discharge in a high-pressure CO2 laser on the pressure has been estimated. The electron density produced by a sliding discharge at pressures up to 8 atm has been measured. The measured electron density is higher than the minimum value of the initial electron density. The frequency of the channels in a multi-channel sliding discharge at high pressure has also been investigated.

The most important optical, thermal, and mechanical properties of KRS (TlBr-TlI and TlBr-TlCl) single crystals were determined. A method for measuring the linear absorption coefficient a and optical strength of these crystals was developed. Typical room-temperature values of a were in the range (6?10)?10?3 cm?1. The thresholds of the surface and bulk damage under the action of cw and pulse CO2 laser radiation were determined. The results indicated that thallium halides were promising materials for laser technology in the ? = 10 ? range.

The results are reported of an experimental investigation of the possibility of using a surface discharge plasma as a cathode in a pulse CO2 laser. A self-sustaining cavity discharge and laser action were achieved in a volume of 0.8 liter at a pressure up to 1.5 atm in the laser mixture. The specific energy output reached 20 J?liter?1?atm?1 when the specific energy input was 165 J?liter?1?atm?1 and the input efficiency was 12%

An investigation was made of the conditions for the formation of an optical breakdown plasma in air when CO2 laser radiation interacted with a polished metal surface in the case of two strongly differing widths of the irradiation spot. Metallographic investigations were made of the surface of the irradiated samples. For the first time, the specific form was established of the surface defects which lowered the breakdown thresholds.

Plasma sheets formed by a creeping discharge on the surface of an insulator were used as a preionization source and as electrodes in atmospheric-pressure CO2 lasers with a cross section of the active medium channel amounting to 150 × 150 mm. The output energy parameters of such lasers were not inferior to those of lasers with electron-beam preionization.

The electrical and output parameters of a high pressure pulsed CO2 laser with plasma cathode are presented. The gain profile is also measured. The use of a sliding discharge as a pre-ionisation source and a plasma cathode permits the achievement of laser action and a high gain coefficient in helium-free mixtures at pressures of up to 8 atm (800 kPa).

A method was developed for tuning a pulse CO2 laser to the 9-μ region. This was done using resonant absorbers placed inside the laser resonator. The pressure in a cell with an absorbing gas was varied from 5 mm Hg to 1 atm. The output in the 9-μ region was comparable with that at λ = 10.6 μ.

A study was made of a nitrogen ultraviolet laser excited by a discharge creeping on the surface of an insulator. It was found that the output radiation from such a laser was characterized by a low divergence and a high power density. Stable operation of the laser was achieved using nitrogen and air at a pulse repetition frequency of 500 Hz without replacing the gas.

The results are reported of a comparative study of ultraviolet spectra emitted from preionization sources designed for gas-discharge lasers. A comparison is made of the emission spectra of a complete surface (guided) discharge, a free spark, and a spark in the presence of an insulator in the discharge region. It is shown that the radiation energy can be concentrated in the required wavelength range by exciting the emission lines of the insulator. The strongest concentration effect is observed for a surface discharge on insulating substrates containing silicon.

A report is given of the results of detailed calculations of the specific output energy of cascade lasing due to 0001–0200–0110 transitions in CO2 molecules pumped by a pulsed gas discharge. The results are given as a function of the initial temperature, pressure, composition of the gas mixture, rate of Q switching of the resonator, and degree of excitation of the CO2(v3) molecules. Under practical conditions the specific output energy at the wavelength of 16.2 μ may amount to 0.2–0.5 J/liter.

An investigation was made of a pulse CO/sub 2/ laser with a nonself-sustaining discharge. When an unstable resonator was used, the energy per pulse was 7.5 kJ. Calculations were made of the dependences of the energy characteristics on the resonator coupling coefficient. The theoretical calculations were in good agreement with the experimental results.

A space-time dependence of the shape of the radiation pulses was observed when the aperture of a laser beam was scanned with a detector. This was attributed to a strong inhomogeneity of the population inversion in the transverse direction of the active medium in a double-discharge CO2 laser. A detailed description of the laser is given.

Two-exposure holographic interferometry was used to study the early stages of evolution of a laser plasma near a target as a function of the residual gas (argon and helium) pressures. The distributions of the electron density were calculated and the pressure "breakdown" thresholds were determined for laser intensities of ~ 1011 W/cm2. The conditions for propagation of an optical discharge near a target were analyzed.

The method of pulse double-exposure holographic interferometry was used to visualize and to study quantitatively a shock wave propagating in a transparent Plexiglas target and initiated by the radiation from a high-power CO2 laser focused on the plane target-vacuum interface. The changes in the refractive index, density of the target material, and the pressure in this material behind the front of a spherical shock wave were determined. Estimates were obtained of the pressure in a plane shock wave and it was found that the efficiency of generation of shock waves by CO2 laser radiation was low. Interference and cumulation of shock waves inside the transparent target, as well as cumulation of an ablation laser plasma near the target were observed. The method could also be used to determine the spatial characteristics of the parameters behind the front of a shock wave initiated by a laser radiation pulse in a transparent target.

It was found experimentally that photoionization of a gas by ultraviolet radiation emitted by a multichannel guided surface discharge generated electrons in a density sufficient for initiation of a high-current nonself-sustained discharge. The use of a surface-discharge plasma as an extended cathode gave rise to a current of 3.6 A/cm2 density in a nonself-sustained discharge in nitrogen. This volume discharge method should find application in high-power CO2 lasers.

An investigation was made of the mechanism of the pressure exerted on plane and hemispherical targets by CO2 laser pulses in air. The optimal laser pulse duration corresponding to the highest values of the specific pressure impluse was determined. The experimental results were interpreted on the basis of a theory of point explosions allowing for the atmospheric counterpressure.

An exprimental study established that the superconducting transition temperature of Nb-Ga, Nb-Ge, Nb-Sn, and Nb-Zr alloys increased as a result of irradiation with CO2 laser pulses. The irradiation took place at room temperature.

A compact high-pressure (8-atm) electric-discharge CO2 laser with a plasma cathode and a working mixture of the composition CO2:N2=1:1 was constructed. Continuous tuning of the emission frequency was achieved in the ranges 938–951, 970–980, 1041–1054, and 1073–1083 cm−1 when the peak power was in excess of 1 MW. The efficiency reached 5% for a nondispersive resonator and the peak power was in excess of 10 MW. The duration of the radiation pulses was 50 nsec.

A high-power Ar–Xe laser (λ = 1.73μ) was pumped by an electron beam alone (j ~ 1A/cm2) and by a combination of an electron beam and an electric field acting on a large volume (30×30×300 cm). An output energy Eout ≈ 9.5J was obtained for the beam pumping (pulse duration τ0.5 ≈ 2.1/μsec) and Eout = 11.5J for the combined pumping. The efficiency, measured relative to the energy deposited by an electron beam, was 0.4%. It was found that additional pumping by an electric field became significant at the onset of nonthermal ionization of the medium and electron multiplication.