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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.

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.

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.

Subgrid modeling of a filtration flow of a fluid in an inhomogeneous porous medium is considered. An expression for the effective permeability coefficient for the large‐scale component of the flow is derived using the scale‐invariance hypothesis. The model obtained is verified by numerical simulation of the complete problem.

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.

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).

Macrodefects of the structure of samples produced by explosive compaction of an aluminum powder were examined. The areas of the new contact particle surfaces produced by high-rate deformation were measured by stereological methods. The eddy current method was used to measure the macroscopic electric conductivity of the compacts. From these data, the mean sizes and number of macrodefects per unit volume of a compact were calculated. The techniques employed can be useful for an analysis of the structure of composite materials produced by various methods.

Electromagnetic processes in flat thermocouples made of metals with varying conductivity under conditions of dynamic loading with a traveling load are studied. The distribution of the electric potential over the thermocouple surface is shown to carry information on the velocity field and the strained state of the thermocouple materials. An experimental procedure for validating various theoretical models of continua under high-velocity deformation is proposed. As an illustration, results of numerical simulations for flow of an ideal incompressible fluid are presented.

Compaction of a powdered aluminum alloy reinforced by high-strength metallic and ceramic fibers in a flat layer under a running explosive loading is studied. The values of the compaction pressure of the matrix material and of the failure pressure of ceramic fibers are found. The structure of the compacts obtained and the character of failure are analyzed.

A simple and sufficiently accurate method is proposed for estimating the parameters of shockwave loading of porous materials under conditions of complete compaction of the material to the density of a monolith.

The foil-method and metallographic studies of powdered material particle orientation in specimens subjected to loading are used to show that upon regular reflection of colliding shock waves the flow in the region where they branch is homogeneous. A well expressed high-speed flow of material behind the Mach wave from exists for irregular reflections. In the shock wave branching region, two qualitatively different flowregimes are possible: without high-speed flow slippage, and with such slippage. Flow without slippage is found at shock wave amplitudes below some threshold value, dependent on the initial density of the powdered metal. A transition zone in the form of a viscous wake exists at the boundary of the high-speed and low-speed flows. A numerical solution of the model problem of mixing of two homogeneous flows of viscous liquid was carried out. By comparing calculation results to experiments which recorded characteristic viscous wake parameters, it was established that the effective viscosity of a shock-compressed copper powder with dispersion < 60 μm comprises ∼0.01 m2/sec, with the material remaining in the solid state at a density close to that of a monolithic specimen.

A method has been developed for measuring the temperature of a cumulative jet using the thermoelectric effect. The temperature of a copper jet formed under shock loading of a specimen with a semispherical cavity has been measured.

Methods and results of tests of biomedical parameters of a new accessory circulation apparatus based on implantable axial blood pump are discussed in this work. Bench tests were directed toward determining energy parameters and pump-induced injury of blood cells. The results of the tests allowed efficiency of the developed system to be evaluated within a wide range of working load.

Thermoelectric effects in a bimetal plate loaded by a gliding detonation wave are explored. The electric–potential distribution is measured on the surface of such a thermocouple which is nonuniformly heated as a result of high–rate deformation. Experimental results are used to determine the stress state of the metal and are compared to calculations performed within the framework of the Mie—Gruneisen model.

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 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.

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.

The main purpose of explosive compaction of porous reinforced and nonreinforced materials is the obtaining of strong compacts with the density close to the monolithic density. As is known, only the dynamic regime of explosive compaction allows for the solution of the problem. This way, the increase in the accuracy of calculation of the pressure value in a porous material results in the possibility of a more optimal selection of the initial loading parameters to provide the dynamic compaction regime throughout the depth of the sample under consideration. We present a technique for rough estimating loading parameters in powder materials for the case of strong shock waves. The comparison of the experimental results with the calculated shape of the shock wave has shown that the discrepancy of the results does not exceed 5%.

A number of time analyzing image converter tubes integrated with thinned, backside- illuminated, electron-bombarded (EB) CCDs were developed. Among them are PV001, PV003, and PIF01 streak tubes, differing from each other by their internal electron optics and external (metal-glass or metal-glass-ceramic) geometry. All tested EB CCD/streak tubes reveal relatively good behavior due to the long-term stability of their input S1 photocathode and reproducibility of the matrix parameters. These tubes differ advantageously from their regular type phosphor screen analogs by their rather high spatial resolution (40 lp/mm at 10 MTF for PV type tubes and 25 lp/mm at 10 MTF for PIF type tubes), reasonably good threshold sensitivity of 10-10 J/cm2 in standard, 10 MHz CCD scanning mode at 850 nm input radiation, and picosecond temporal resolution (better than 5 ps) at a relatively acceptable value of the light transfer function (approximately 102).© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

It is well known that thinned backside-illuminated CCD image sensors are very efficient for electron beam imaging. The authors have adapted an electron-bombarded (EB) CCD for application in UV and VUV spectral regions. This adaptation includes the creation of a shallow accumulation layer near the device backside surface either by ion implantation and annealing or by a certain chemical treatment of the surface. Preliminary experimental results confirm the applicability of the developed procedure in achieving a reasonable quantum efficiency. Some problems associated with the UV and VUV imagers design and fabrication are discussed.

A luminescence screen was replaced with a thinned, backside-illuminated, electron bombarded (EB) CCD in a well-known PV 001 streak/shutter image converter tube. The tube was mounted into an experimental camera prototype for measurement of its main technical characteristics. Under EB CCD readout operation in a free-scanning, slow-speed mode, the overall system spatial resolution was higher than 40 lp/mm at 10% MTF, and the linear part of the light transfer function was not less than 130. In streak mode the PV 001/EB CCD image tube exhibited threshold sensitivity of not less than 10-10 J/cm2 when recording 40 ps, 850 nm radiation pulses from a semiconductor laser. The preliminary results indicate that the PV 001/EB CCD image tube has quite a stable infrared sensitivity of its S1 photocathode.

Possibilities of EB CCD sensors application for electron-optical picosecond recording systems have been investigated. Some requirements for the EB CCD fabrication procedure were theoretically established and experimentally confirmed. EB CCD sensors were inserted either into the first generation image intensifiers coupled through fibre optics plate to the output of the temporal analysing tube or directly instead of the phosphor screen of this analyser. In the second case the system spatial resolution is slightly better while the sensitivity for both systems is almost the same.

In the optical channel of picosecond recording system a set of cross-over image tubes and microchannel intensifiers were used together with either light sensitive cooled CCD-image sensor (520. JC pixels) or electron-bombarded CCD installed inside cross-over type image tube, or SIT-vidicon sensor. 4.5±0.5 Ps light pulses from YA1O3 :Nd laser at l.O8jum wavelength, and 2 Ps light pulses from AlGaAs/GaAs semiconductor laser at 850 nm wavelength were employed for comparative measurements of the recording system. It is shown that the electron-bombarded CCD matrix placed inside cross-over type image tube and matched through fibre optics window directly to pv-oo1 temporal-analysing image converter tube, provides the overall system spatial resolution of 25 line pairs/mm at 30% MTF, dynamic range of not less than 50 and input photocathode sensitivity about 2E-1O J/cm**2.

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.

The author heated specimens of steels U8, U10, 12KhNZA, 30KhN2MFA, 20KHNZA, 18Kh2NZA, 18Kh2N4VA and 50 to 860 - 900 C. The specimens were subjected to elastoplastic bending, quenched by symmetrical cooling in water or oil. Specimens of steels 30KhN2MFA and 18Kh2N4VA were preliminarily cooled to 400-500 C and subjected to elastic bending. The deflection after final cooling remained fully fixed. The results of experiments provide grounds for asserting that during the process of martensic transformation the elastic deformations caused by external forces as well as by thermal stresses completely change into plastic deformations. This is of decisive importance in the process of formation of residual stresses, and especially of stresses in parts subjected to heat treatment.

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.

Composite materials (CM) of layered, fibrous, and porous structure open up considerable possibilities for constructing materials exhibiting a comprehensive set of properties [i]. Currently a number of experimental works are known devoted to questions of preparing reinforced CM using welding of metals by explosion [2-4]. In the mechanisms established for reaction of reinforcing fibers with matrix plates with a glancing explosive load, the required and adequate conditions for forming a strong joint of the fiber with the matrix have been determined, and the typical structures and properties of the interphase boundary have been studied.

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.