Gaseous Active Medium Research Articles

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ РАСПРОСТРАНЕНИЯ ПУЧКОВ ЛАЗЕРНОГО ИЗЛУЧЕНИЯ В НЕРАВНОВЕСНОЙ ДВИЖУЩЕЙСЯ ОБЛУЧАЕМОЙ НЕЙТРОНАМИ ПЫЛЕВОЙ ПЛАЗМЕ, СОДЕРЖАЩЕЙ НАНОЧАСТИЦЫ УРАНА

The use of uranium nanoparticles dispersed in a laser-active medium instead of traditionally used methods of heterogeneous nuclear pumping of active gas medium can increase the fraction of energy carried by fission fragments from the condensed phase into the gas medium by more than an order of magnitude. This creates the conditions for increasing the efficiency of nuclear into optical radiation energy conversion. However, the scattering and absorption of laser radiation by an active medium containing uranium nanoparticles are important factors preventing the laser radiation generation in such a medium. Mathematical modeling of the generation and amplification of laser radiation in a moving spatially inhomogeneous nuclear-excited neutron-irradiated argon-xenon medium containing uranium nanoparticles injected into a cylindrical laser-active dusty element, taking into account optical inhomogeneities caused by the dust component. The process of amplification and intensity distribution of a master oscillator laser beam in a moving spatially inhomogeneous nuclear-excited argon-xenon neutron-irradiated medium containing uranium nanoparticles has been studied for the first time. Data were also obtained on the propagation of a light beam near a relatively sharp dust component concentration decrease in moving gas medium. As a brief result: moving spatially inhomogeneous nuclear-excited neutron-irradiated argon-xenon medium containing uranium nanoparticles does not have a pronounced destructive effect on the propagation of laser radiation in it, on condition that the light flux is not wider than the dust component.

MODELING OF DIFFUSION COATINGS STRUCTURE WITH VANADIUM AND TUNGSTEN IN COMPOSITION-FILLING ENVIRONMENTS

The process of modeling the production of vanadium and tungsten coatings is an effective method of increasing the reliability and durability of machine parts, tools by creating protective layers on the surface of the workpiece, which have a unique set of physico-chemical properties.One of the most effective methods of developing protective layers having high mechanical, physical and chemical characteristics is the diffusion saturation of the surface of the layers using composite powder materials.The formation of protective coatings in composite saturation media occurs under non-stationary temperature conditions. The method of diffusion saturation of the solid phase surface in the active gas medium is based on the analysis of the requirements for the diffusion layer and the method of metal saturation is selected. The rates of chemical processes are determined by kinetic regularities that depend on both temperature and diffusion factors. This method provides high surface quality, is the simplest and most used in laboratory practice, reproduces well in production conditions, and does not require special sophisticated equipment to implement it.

New gas-discharge pulse laser on electronic transitions of neutral neon atoms with a wavelength of 743.89 nm

For the first time, the new visible pulse gas-discharge laser was created on electronic transitions of neutral neon atoms with the radiation wavelength of 743.89 nm pumped by a self-sustained volume transverse electric discharge with UV preionization of a high-pressure active gas medium. Spectral, energy and temporal characteristics of the new laser source are investigated. The laser energy was 0.4 mJ with the pulse duration of about 12 ± 1 ns (FWHM). In this case, the peak laser power was more than 32 kW. The divergence of laser radiation was about 0.3 mrad.

Effect of the Built-in Surface Potential on the I–V Characteristics of Silicon MIS Structures

The regularities of the modification of I–V characteristics of MIS structures via forming built-in surface potentials induced during the fabrication of an atomically pure silicon crystal surface using microwave plasma micromachining in different chemically active gaseous media are investigated. The effect of surface potentials on the slope of the I–V characteristics of the MIS devices and the value of their asymmetry at the reversal of the gate polarity are established. The increase in the slope of the I–V characteristics is attributed to the weakening of the diffuse scattering of electrons during the formation of negatively charged surface trap states at the interface and an increase in their mobility in the space charge layer at the semiconductor surface.

Improving abrasive tool cutting properties with the use of impregnators that emit chemically active gas media during thermal decomposition

Abstract Impregnation is one of the most commonly used methods of supplying microdoses of lubricant to the cutting zone. The expediency of using substances capable of releasing chemically active gas media, in particular, halogens and chalcogens, during thermal decomposition in the cutting zone as impregnators is substantiated. Application of the recommended compositions as abrasive tool impregnators provides reduction in cutting force components, abrasive tool wear and roughness of the processed surface. The local microprobe analysis demonstrated a reduction in the transfer of abrasive material to the treated surface. Production tests confirmed the effectiveness of the new impregnators.

New front-end electronics for [formula omitted]-[formula omitted] experiment

The India-based Neutrino Observatory (INO) is an underground experimental facility housing high energy and nuclear physics experiments. A 50 kton magnetized Iron Calorimeter (ICAL) detector is the flagship experiment at this facility. The primary goal of ICAL experiment is to determine the neutrino mass ordering using atmospheric neutrino events. The detector will consist of 151 alternating layers of iron and Resistive Plate Chambers (RPCs). The iron will provide the active target for the atmospheric neutrinos to interact, whereas the RPCs will help in detecting muons and hadrons produced from such interactions. The signal produced due to the muon interaction with the active gas medium in the detector will be extracted using a two-dimensional readout of the RPCs. The complete ICAL detector will have approximately 3 million channels to be readout. Such a large number of channels require an efficient, robust and cost-effective readout system. A semi-digital readout system HARDROC2 has been tested and commissioned to its possible use for ICAL experiment. The HARDROC2 chip is fabricated using 350 nm SiGe technology and characterized by 64 channel readouts with low power consumption. In this paper, we propose a new front-end electronics based on HARDROC2 ASIC for the ICAL experiment. We report the results obtained from a detailed study performed to optimize the various performance parameters like channel calibration and uniformity using the test bench setup. We also provide the efficiency and cluster size results obtained for ICAL RPC detectors with HARDROC2 based readout and compares the same with the one obtained with custom electronics.

A Highly Stable Source of Current Pulses with an Adjustable Amplitude of up to 350 A for a Nonlinear Complex Load

The application of high-power semiconductor lasers for creating a population inversion in active gaseous media is an integral part of studies that are aimed at the achievement of a sufficient level of laser-radiation energy to initiate a thermonuclear reaction. The stability of the laser radiation and, thus, the repeatability of experimental results, depend on the stability of the parameters of current pulses for pumping laser-diode arrays with a pulse amplitude of up to several hundred amperes. The flow of current pulses with such an amplitude through a cable that connects the load to the output of the current-pulse source must not lead to the formation of voltage pulses of opposite polarity across the load, which can damage it. This can be prevented by correcting the current pulse edges. It is proposed to develop a source of current pulses with a high amplitude on the basis of several modules of fast linear current amplifiers with individual control loops, whose outputs are connected in parallel. It is established that a compensation-type current sensor on the basis of the Hall effect is operable at high frequencies and can be used in these modules, but it has pronounced resonance properties, which must be canceled. It is shown that analog driving pulses of each module can be formed using aperiodic chains with parameters that eliminate oscillatory processes in the load circuit. A dynamic model of a module of the linear current amplifier and the calculation relationships for the parameters of its components, which follow from this model, are presented. The experimental results that confirm stability of the parameters of the formed current pulses are presented.

Pulsed microwave discharges in powder mixtures: Status, problems, and prospects

Results of experiments on the excitation of pulsed microwave discharges by gyrotron radiation (λ = 4 mm, P0 = 100–500 kW, τ = 1–10 ms) in the volumes and on the surfaces of metal-dielectric powder mixtures are presented. It is shown that there are two phases of discharge development: the spark phase, accompanied by a partial evaporation of the powder material, and the phase of a developed discharge, characterized by a plasma density of ∼1017 cm–3, high absorption, and high temperatures (∼5–10 kK) in a thin layer (∼0.1–0.2 mm) of plasma and vapor. It is demonstrated that the conductivity induced in the targets by UV radiation play an important role in the microwave absorption by powder grains. It is found that, in the course of the discharge, a conductive metal mesh forms in the powder volume as a result of metal evaporation. Reactions of high-temperature synthesis were initiated in various powder mixtures (Ti + B, Al + Fe2O3, Mo + B, etc.). It is shown that the reactions of high-temperature synthesis last for up to 0.1 s and are accompanied by the evaporation of powder grains and the formation of an aerosol cloud due to free expansion of reactants from the sample surface. The possibility of experimentally studying the kinetics of reactions of high-temperature synthesis is demonstrated. It is noticed that microwave discharges can be used to initiate plasmachemical reactions on the surfaces of radioparent materials in active gaseous media.

Development of a 1J short pulse tunable TEA CO2 laser with high energy stability

Abstract The design, development and operational characteristics of a 1 J, repetitively pulsed, line tunable TEA CO2 laser producing nearly tail free short pulses (~170 ns) suitable for laser isotope separation is discussed. Tail free short laser pulses were generated by employing a nitrogen lean gaseous active medium. Use of an indigenously developed stable pulsed power supply, uniform and intense UV spark pre-ionization and optimum gas purging with catalytic regeneration to control the deleterious oxygen accumulation helps generate laser pulses with high energy stability. Integration of a sensitive arc detection system allows long term arc-free operation of the laser and protects it from catastrophic failure. Laser pulses in more than 90 lines in 10.6 µm and 9.6 µm bands of CO2 laser spectrum with energy about 1 J in as many as 50 lines could be generated with a typical efficiency of about 4%. A typical pulse to pulse energy stability of ±1.4% was obtained during one hour of continuous operation of the TEA CO2 laser at 75 Hz.

Model of structural zones of the TiN and TiAlN coatings formed by the arc evaporation of metal in an active gas medium

The role of temperature and temporal conditions of ion cleaning is revealed and optimal process and temperature modes of its performance before the formation of the Ti-Al-N-based films with a homological temperature no higher than 0.22Tm.f are established. It is determined that, during film deposition, each variable process parameter in the range under study increases the film temperature to some extent and affects the rate of its formation stages and the process of structure formation. Integrated models of structural zones of the Ti-Al-N-based and TiN films formed by the arc method are constructed for the qualitative description and prediction of the structural evolution of the film depending on the process and temperature parameters of the preparation and deposition.

Magnetic field interaction with guided light for detection of an active gaseous medium within an optical fiber

We report a novel fiber-optic sensing architecture for the detection of paramagnetic gases. By interacting a modulated magnetic field with guided light within a microstructured optical fiber, it is possible to exploit Faraday Rotation Spectroscopy (FRS) within unprecedentedly small sample volumes. This approach, which utilizes magnetic circular birefringence and magnetic circular dichroism effects, is applied to a photonic bandgap fiber to detect molecular oxygen and operates at a wavelength of 762.309 nm. The optical fiber sensor has a 4.2 nL detection volume and 14.8 cm long sensing region. The observed FRS spectra are compared with a theoretical model that provides a first understanding of guided-mode FRS signals. This FRS guided-wave sensor offers the prospect of new compact sensing schemes.

Pumping of electromagnetic energy via multiple total internal reflection from active media

An experiment for strong light amplification at multiple total reflections from active gaseous media is proposed.

A proposed experiment on ball lightning model

We propose an experiment for strong light amplification at multiple total reflections from active gaseous media.

A comparative study on thermal lensing characteristics of low (∼500 °C) and high (∼1500 °C) temperature variants of copper vapor laser

This paper presents a comparative study on thermal lensing characteristics of a low temperature copper vapor laser (CVL) (LT-CVL as Copper-HBr laser) and a high temperature CVL (HT-CVL as elemental CVL). Interferometric techniques were used to study the combined thermal lens power of active gaseous medium and discharge sealing optical windows as well as that of the optical windows separately at different electrical input powers. As the input power varied from 2.7 to 4.6 kW, the combined thermal lens power varied from −1.4 to +0.94 km −1 for LT-CVL and from +1.4 to +13 km−1 for HT-CVL. The thermal lens power of the windows varied from +3 to +15 km −1 for HT-CVL. On the other hand, for LT-CVL, the thermal lens due to windows was very weak and could not be measured. It was observed that the origin of net thermal lensing mostly resides in the discharge tube windows owing to its higher temperature variation of refractive index as compared to that of gaseous active medium. The weaker thermal lens characteristics of an LT-CVL was attributed to its much lower working temperature and relatively flatter radial gas temperature profile than that of an HT-CVL.

Special features of refining processes in welding aluminized steel with an oxidizing gas

Aluminium content reduction in the weld metal occurs as a result of aluminium oxidation in the weld pool and precipitation of aluminium oxide into slag at welding aluminized steels in active gas and gas mixtures. Additional feed of highly oxidizing gases from the other side of the welding bath at welding in active gaseous medium allows for reaching an even reduction of aluminium content in the weld metal and for improving the mechanical characteristic of the welded joints from aluminized steels.

Special features of aluminium-coated steels in active gas media

It is established that weld metal saturation by aluminium occurs at welding steels coated by aluminium, and this decreases mechanical properties of the welded joints substantially. Application of the gaseous medium with high oxidizing ability at welding allows for refining weld metal from aluminium and for improving strength and plastic properties of the aluminium-coated steel welded joints.

Features of the pulsed inductive discharge formation for pumping gas-discharge radiation sources

The process of pulsed transverse inductive discharge formation has been experimentally studied depending on the parameters of an active gaseous medium and a discharge excitation circuit. It is established that optimum conditions for obtaining inductively coupled plasma in a transverse vortex field that excites the gaseous medium are achieved by excitation inductors with inductances of 50–300 nH, to which up to 30% of the energy of a pumping LC oscillator can be transferred. It is concluded that the energy stored in these excitation inductors can be effectively used in spontaneous and coherent radiation sources.

Photolytical XeF(C–A) laser amplifier of femtosecond optical pulses: gain measurements and pump efficiency

Gain characteristics of a photolytically driven XeF(C–A) laser amplifier are studied experimentally in the unsaturated amplification regime. The gaseous active medium is optically pumped by vacuum-ultraviolet (VUV) radiation from two large-area multichannel surface discharges initiated along opposite walls of the amplifier chamber. A total gain factor of 102 is obtained for the ultrashort optical pulses under multipass amplification in the active volume of 40 × 18 × 4 cm3 dimensions with a spatially homogeneous gain distribution. Spectral measurements reveal a good conservation of the seed pulse spectrum. Small-signal gain reaching 2×10-3 cm-1 is observed for the blue-green seed pulses of 150 fs duration, as well as for the continuous seed radiation at 488 nm. The obtained gain values, being compared with the gain calculated for the measured pumping radiation power, indicate that the quantum yield of the XeF(B) formation as a result of the XeF2 photodissociation is high and approaches unity within the spectral band of the XeF2 VUV photodissociation continuum.

Electron-beam pumping of excimer media in a multipole magnetic field. 1. Numerical simulation of the energy input

A scheme of the system for pumping active gas media by electron beams injected into a gas volume located in a multipole magnetic field is proposed and engineering solutions are presented, which were used in the development and making of this system. The possibility of changing a resistance to a plasma current initiated by a relativistic electron beam is promising for the additional control of the kinetics of processes in the active gas medium with the aim of increasing the energy input efficiency. The scheme proposed in the paper allows the combination of the pumping of the gas medium by an electron beam with pumping by a controllable discharge initiated by this beam in electric fields of the beam. The energy input of electron beams to the gas medium located in a quadrupole magnetic field is analysed by the Monte-Carlo method. The calculations demonstrate a high efficiency (90%) of the beam energy transfer to the gas and the possibility to control the energy-input profile.

Small pad RPCs as detector for high granularity digital hadron calorimetry

Requirements for sampling hadron calorimetry with gaseous active medium and digital read-out for a future linear e+e--collider (FLC) are formulated. Monogap glass Resistive Plate Chamber (RPC) prototypes equipped with 1cm2 read-out pads and operated in saturated avalanche and streamer modes are studied as a possible detector for digital hadron calorimetry. Operating characteristics of the prototypes such as induced charges, efficiencies and fired pad multiplicities are measured for different gas mixtures, gas gap widths and anode thicknesses, electronics thresholds, beam incident angle and intensity. Choice of RPC working performance is outlined.