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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.

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.

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.

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.

A system of dissipative modes in an incompressible flow of space dimensions d>or=2 is considered. The self-induced phase chaos is shown to arise in the motions of very small scales, which are fed by the large-scale ones through repeated nonlinear interactions. This property is used to derive the equations for the Fourier amplitudes. Solutions similar to those derived previously for turbulent fluctuations in the dissipation range are obtained. Properties of the short-scale intermittency are analysed. The authors show that no coherence and intermittency can be built up at asymptotically high wavenumbers.

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 energy of the fully developed turbulence is excited at some large scale and is transferred through the inertial range to the viscous scales. While the transfer, the spatial intermittency is growing up and the small scale fluctuations occupy very small fraction of space [1]. Natural theoretical framework for the non intermittent pulsations is the original Kolmogorov (1941) scaling hypothesis [1] and the renormalization group technique [2], [3], [4], [5]. Intermittency induces corrections to simple scaling. Teodorovich [6] studied intermittency corrections by analyzing the infrared divergence within the framework of the field-theoretical renormalization group.

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.

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.

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 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%

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 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 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 straightening-stretching machine has been designed at the All Union Design and Research Institute for Chemical Engineering. It straightens metal strips in the cold state by stretching beyond their limit with a maximum extension deformation of 3%. A sketch indicates stand, drive for untwisting strip, power cylinder, slide block, and front clamping head, among other aspects of the machine. The technical characteristics are specified and the process is explained. The economy affected on introducing the straightening-stretching machine is indicated.

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.

An experimental study was made of the repulsion of bodies by the surface of water interacting with laser radiation. A beam from a pulse CO2 laser incident obliquely on the surface of water threw upward a body located above the illuminated spot. In a second experiment a beam from an unswitched pulse neodymium laser entered water from below and lifted momentarily various bodies to a height of several meters. The specific momentum of the bodies per unit laser energy was determined. It was concluded that the effect could be used to produce optically a vapor cushion which would make possible levitation, flight, starting, and acceleration of a body in a laser beam above a water surface.

A study was made of the possibility of reducing the duration of output pulses of atmospheric-pressure CO2 lasers by quenching stimulated emission (as a result of intracavity breakdown) and pulse sharpening (as a result of extracavity burning of metallized films). Pulses of 10 nsec duration at midamplitude with 3–4 nsec edges were obtained in this way.