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A time-dependent model of laser amplification in an Yb : YAG crystal is considered based on a system of balance equations, as well as radiation transfer and heat conduction equations. The model also takes into account the dependence of the laser characteristics of the gain medium on the injection wavelength and the effect of amplified spontaneous emission. This model is verified based on a diode-pumped amplifier with cryogenic cooling of active elements. The dependences of the gain on the pump pulse energy are experimentally measured for different amplification regimes and compared with simulation results.

Aim. To study changes in epithelialization of diabetic foot ulcers and parameters of laser Doppler flowmetry (LDF) in patients with diabetic foot syndrome (DFS) and atrial fibrillation (AF) during complex therapy with the addition of direct oral anticoagulants (DOAC).Material and methods. An open-label comparative randomized study in parallel groups was performed. Patients with neuroischemic DFS and persistent FA without previous anticoagulant therapy were randomized into two groups: combination therapy for DFS and rivaroxaban (group 1; n=24) or combination therapy for DFS and dabigatran (group 2; n=22). Changes in local status in diabetic foot ulcers, coagulogram parameters and LDF were studied at 4 and 12 weeks.Results. Complete epithelialization of diabetic foot ulcers after 12 weeks was found in 14 (58.3%) patients in group 1, and in 10 (45.4%) patients in group 2. Statistically significant improvements in LDF parameters were found in both groups in both groups: an increase in the microcirculation index by 53.5% (p=0.02), pulse wave by 124.0% (p=0.003), respiratory wave by 59.4% (p=0.007) was found in group 1. An increase in the microcirculation index by 48.5% (p=0.02), pulse wave by 73.1% (p=0.003), respiratory wave by 47.1% (p=0.03) were found in group 2.Conclusion. Positive statistically significant changes in epithelialization of diabetic foot ulcers and LDF parameters were found in patients with DFS and AF during 12 weeks of complex therapy with the addition of DOACs (rivaroxaban and dabigatran). Further research for DOACs in DFS patients is needed.

A time-dependent three-dimensional model for the laser amplification process has been constructed with allowance for the effect of the temperature distribution on the thermophysical and lasing characteristics of gain media. We have performed numerical modelling of the laser amplification process in the gain elements of a two-stage subjoule-level cryogenic laser amplifier operating at a pulse repetition rate of up to 1 kHz. It has been shown that taking into account the temperature distribution is of critical importance in calculation of cryogenically cooled laser amplifiers pumped with high-power diodes. We have found optimal diode pump parameters at which the maximum achievable pulse energy at the amplifier output can reach 300 and 570 mJ at pulse repetition rates of 1000 and 500 Hz, respectively.

The dependence was studied of the level of density fluctuations recorded at different devices on the minor and major radii of the tokamak. It is known that a high level of density fluctuations can negatively affect the operation of diagnostics, in particular, the plasma reflectometry diagnostic. The increase of density fluctuations decreases the quality of raw data by increasing the error of measuring the density profile and, when density fluctuations exceed the threshold value, it renders such measurements impossible. Based on experimental data obtained on devices with substantially different sizes, a dependence of the density fluctuation level on the major and minor tokamak radii was proposed. Since the main experiments were carried out in round limiter tokamaks in ohmic (OH) heating regimes, the extrapolation result is applicable, generally speaking, to installations of larger size with the same configuration and regimes. However, experiments with electron cyclotron heating at the T-10 tokamak also allow one to extend the obtained dependence to regimes with auxiliary heating. It was shown that the obtained dependence is applicable to limiter tokamaks Tore Supra and TFTR of larger size. The applicability of the dependence to installations with diverter configuration is discussed and the possible level of density fluctuations is extrapolated to the international reactor tokamak ITER that is being constructed in France.

Background and Objectives: The traveling wave thermoacoustic engine is a variation of the Stirling engine family. With an increase in the number of stages of a traveling wave thermoacoustic engine from one to four, an improvement in the characteristics of the acoustic wave in the regenerator zone is observed, the temperature difference between the heat exchangers required to start the engine decreases, and theefficiency increases. For this reason, it is important to study the patterns of changes in engine characteristics with a further increase in the number of stages. The aim of the work was to study the influence of the number of stages on the characteristics of the acoustic wave in the engine. Materials and Methods: A numerical calculation of eight models of engines with the number of stages from three to ten was carried out in the Delta EC program. The working gas is argon under a pressure of 1.5 MPa, the diameter of the heat exchangers is 160 mm, the diameter of the acoustic resonator is 41.2 mm, the length of the looped engine resonator for all models was 8 meters. The stages in all engines were structurally the same. In the course of the calculations, the number of stages and the number of acoustic loads changed, while maintaining the same total length of the hull-resonator. For each of the eight models studied, the acoustic load was optimized to achieve the maximum engine efficiency. Conclusion: It was shown that with an increase in the number of stages from three to ten, there is a gradual increase in the phase difference between the pressure and velocity oscillations, that is, the wave approaches the parameters of a standing wave in the entire cavity of the resonator. In this case, the maximum acoustic load power and efficiency were observed when the number of stages was equal to five. With an increase in the number of stages from five to ten, the power of each individual stage decreased by 15.8%, and the efficiency decreased by 8%.

Intracerebral hemorrhage (ICH) is severe and fatal complication of anticoagulant therapy with an incidence 0.3-0.7% per year. For patients with atrial fibrillation (AF) anticoagulants are administered for decreasing risk of stroke and systemic embolism. In this case the occurrence of intracranial bleeding is hard task for doctor. From the one side it is necessary to reverse the action of the drug for preventing the growth of hematoma. At the same time the discontinuation of therapy increases the risk of systemic embolism for patients with AF significantly. Clinical guidelines and studies have been reviewed about ICH during anticoagulant therapy. Nowadays there is no quality evidence about reversal of anticoagulant effects after ICH and optimal time of resumption of anticoagulant therapy. Firstly, we do not have large randomized controlled trials on this issue. The majority of clinical guidelines were based on retrospective studies and opinions of experts. Soon several randomized controlled trials will be finished and new data will be presented.

In modern large-sized tokamaks and those under construction, for example, in ITER, when measuring the average plasma electron density using the refractometry technique, it becomes necessary to study different effects that affect the measurement accuracy. This paper presents the results from studies of the high-temperature effects that can affect the interpretation of delay time measurements of the probing microwave signal in the ITER refractometry diagnostics. The criteria for applicability of different plasma models (“cold” plasma, modified “cold” plasma, and “hot plasma”) are obtained for calculating the plasma refractive index and interpreting the delay times that will be measured using the refractometry diagnostics of the ITER plasma. In the second article, based on the results obtained in this article, we will consider the influence of the high-temperature effects on the accuracy of determining the mean density using the refractometry diagnostics.

The prospects of composite materials based on polymer matrices with the inclusion of carbon nanotubes, including oriented carbon nanotubes, as both functional and structural materials for nanosatellites are considered. The thermal conductivity and electrical conductivity of the composites has been measured. Techniques for producing carbon nanotubes, including vertically oriented nanotubes synthesized on filaments, and coaxial regular nanomesostructures as a functional additive for varying the properties of materials are proposed.

The Moscow University Universat-SOCRAT program is aimed at using small satellites to monitor space threats, such as radiation in near-earth space, electromagnetic transients, and potentially dangerous bodies of natural and artificial origins. The first stage of the program implementation began on July 5, 2019 as a result of the successful launch of three Cubesat-type nanosatellites from the Vostochny cosmodrome. These satellites are equipped with instruments for space radiation monitoring, as well as prototypes of devices for observing transient phenomena in the Earth’s atmosphere. In particular, two satellites are equipped with scintillation phosphich detectors that detect charged particles and gamma quanta in the energy release range of 0.1–2 MeV. The geometric factor of these instruments is $${\approx}50$$ cm $${}^{2}$$ sr. One of the Cubesats also carries an optical photometer, consisting of four silicon photomultipliers, which entrance windows are covered with different light filters. The satellites were launched into solar-synchronous orbits with an altitude of $${\approx}550$$ km. This makes favorable conditions for space radiation monitoring in various areas of near-Earth space, including zones of trapped radiation, areas of precipitation, etc. Such an orbit also allows observations of flare phenomena both in the equatorial atmosphere and at high latitudes. The first results of flight tests are discussed.

The results on the analysis of methods for the formation of nanoscale elements on thin films of chalcogenide glassy semiconductors and their application to create optical diffraction elements are presented. When creating micro- and nanoelements of optoelectronic devices, micro / nanoelectromechanical systems (MEMS/NEMS) and diffractive optical elements, chalcogenide glassy semiconductors (CGS) can be effectively used. The use of CGS is mainly based on their sensitivity to various types of radiation, which cause structural changes in them and transparency for infrared light. Numerous studies have been carried out aimed at studying the processes of formation of nanostructures on CGS films. A number of photoinduced changes are observed in CGS, which are associated with structural transformations, phase transitions, defect formation, and atom diffusion. It is of interest to determine the technologies for the formation of micro- and nanoscale structures on CGS films that can be used to create diffractive optical elements for optoelectronic devices. Increasing the resolution of recording media based on vitreous chalcogenide semiconductors can be achieved by choosing recording modes and glass compositions, in which the nonlinearity of the exposure characteristics of photosensitive material is most pronounced, as well as the introduction of noble metal nanoparticles for excitation of precious metals for excitation. A promising area of application of chalcogenide glassy semiconductors can be direct laser recording of diffractive optical elements at upgraded laser beam recorder of master disks. The unique properties of chalcogenide glassy semiconductors allow the formation of microrelief images without selective chemical etching due to the irradiation of thin films with rays of different polarization. Fig.: 8. Refs: 41 titles.

This paper considers an original valve electromagnet with integrated armature, designed to implement an electromagnetic overcurrent release of a circuit breaker. Theoretical and experimental studies of the proposed electromagnet have been carried out to determine the most important parameters of circuit breakers such as sensitivity and high-speed performance. Calculations and experiments have shown the possibility of increasing the sensitivity and speed of the electromagnetic overcurrent release based on the proposed electromagnet with integrated armature in comparison with existing structures used in modern circuit breakers.

Reduction of optical quantum sensors in size, including nuclear magnetic resonance (NMR) gyroscopes, implies primarily downsizing of the working gas cell. This paper considers the dependence of isotope shift in the balanced scheme based on NMR in xenon isotopes on the dimensions of the gas cell. With this aim in view, an experimental and theoretical studies of the factors affecting the relaxation rate of xenon isotopes have been carried out. The proposed numerical model allows predicting the magnitude of the isotope shift for cells of various sizes with variations in their basic parameters, namely, temperature and pressure of the gas mixture. Based on the results of the numerical simulation, recommendations are given for optimizing the basic parameters of the gas cell by changing its dimensions.

The influence of reflective Bragg gratings that are formed in an active medium due to the spatial periodic modulation of gain on the spectral properties of lasing are investigated by an example of a pulsed Nd : YAG laser. It is shown that, at a certain choice of the formation regime of reflective gratings of gain, the lasing bandwidth can be reduced by a factor of 3 – 5, with a corresponding increase in the pulse energy and significant improvement of spatial beam quality.

The purpose of this work is to study the effect of rapid thermal annealing (RTA) with halogen lamps on the structural and phase characteristics of lead zirconate-titanate (PZT) films. The PZT thin ...

Methods to create microrelief phase elements for diffractive optics and ophthalmology were analyzed. Direct laser writing, by a laser beam recorder used for master discs is an effective method for the formation of flat microrelief phase elements on thin films of chalcogenide semiconductors, where photo-structural transformations occur under the action of laser radiation.

The methodology of determining the surface temperature of composite materials with unknown emissivity is studied. The methodology is implemented by using a standard sample of spectral normal emissivity over the range of wavelengths 1.65–1.80 μm and the industrially produced Metis M322 pyrometer functioning in the same range. The surface temperatures of the composite material under study and platinum, with significantly different values of spectral normal emissivity is determined by the temperature of the standard sample mounted on the materials under study, as measured by the pyrometer. The relative methodological error of determination of the surface temperature of materials under study did not exceed 1.7 and 0.5%, respectively, for the composite material and platinum for surface temperatures approximately 973 K. In the calculation of the error, the results of measuring the surface temperatures of the materials under study were used, obtained taking into account the temperature of the standard sample and in the absence of a standard sample. The imprecision of a priori data regarding emissivity of a standard sample in the interval (–0.01; 0.01) relative to the mean emissivity, equal to 0.19, increases the relative error of determination of the temperature of the composite material by 0.68%. Installation of a standard sample on the materials under study results in temperature modifications on the periphery of the surface, not exceeding 0.47 and 0.05%, respectively, for the composite material and platinum.

The operation of the LM27762 bipolar DC–DC converter chip was simulated using WEBENCH software developed by Texas Instruments. The main attention is paid to the influence of the load current on the negative voltage ripples at the output of the charge pumping system and the chip output. The results of the calculations are compared with the results of the experiments. It is shown that the model of operation of the microcircuit created by the manufacturer is approximate. When the microcircuit operates in burst mode, which is realized at relatively low load currents, the discrepancies in the number of discharge – charge cycles, voltage poles at the output of the pumping system, and in the time intervals between bursts are very significant. The model does not allow obtaining data on the ripples of the negative voltage at the chip output. Experiments have shown that the very limited data on output voltage ripples given in the microchip documentation is underestimated. They significantly depend on the input and output voltage and load currents. The discrepancy between the experimental results and the simulation results obtained using the model of the manufacturer LM27762 showed that the actual perfection test of the microcircuits should be based on three factors: experiment, simulation and joint analysis of the obtained results. The simulation results of the operation of the LM27762 circuit board of bipolar DC–DC converter using the WEBENCH Power Designer software developed by the Texas Instruments manufacturing company are presented. The calculations are made at the company's website. For the experimental studies the ready-for-use test board of LM27762EVM test module, provided by the manufacturer of the LM27762 circuit board, is used. The use of the test board, simulator, and software developed by the manufacturer of the circuit board ensures to have no problem while comparing the simulation and experimental results, which can be associated with the use of circuit components with differing characteristics, or with the board layout. The technical documentation for the circuit board does not have information about the characteristics of the keys and capacitors used in the circuit board. Unfortunately, a description of the developed model is not available either. The information mainly concerns the influence of load currents on negative voltage ripples at the charge pump system output and at circuit board output. The simulation has shown that already at a load current of 40 mA, the control system starts operating with a permanent charge pump frequency, while, according to the results of the experiments, the control system continues to work in the pulse train mode even at a higher current of 50 mA. The pulse train for such current consists of 15 charge transfer pulses, the interval between the trains is 3 μs, and the increase in negative voltage per pulse train is also about 75 mV. The comparison made of simulation results and the results of the experiment have shown that the model of operation of the LM27762 circuit board, created by the manufacturer, is approximate. It has been established that owing to a large number of assumptions in the developed circuit board model, when it operates in the pulse train mode, which is realized at relatively low load currents, the discrepancies are rather significant in the number of discharge–charge cycles, the pulsation amplitude at the charge pump system output, and the time intervals between the pulse trains. The simulation of operation of the circuit board does not give data on the negative voltage pulses at its output. The experiments have shown that the data provided in the documentation on the circuit board output voltage pulses, though quite limited, are underestimated. They largely depend on the input and output voltage and load currents. In general, the comparison of the results of simulation of the operation of the charge pump system of the LM27762 circuit board, when it operates in the pulse train mode, and the corresponding experimental results shows that the coincidence of the calculation results and those of the experiment in terms of quality can be considered satisfactory. The discrepancy between the experimental and simulation results, obtained using the manufacturer’s LM27762 model has proved that the true testing of the quality of circuit boards requires three factors to be taken into consideration: experiment, simulation and joint analysis of the obtained results.

A high peak and high average power femtosecond laser system based on media doped with Yb3+ ions is being developed at the Institute of Laser Physics of the SB RAS. For efficient laser amplification and to avoid optical damage is actually to compensate wave front distortion caused by grating astigmatism in pump channel. Based on theory of propagation of gaussian beam in space and through optical elements the calculation of optimal parameters of two lenses telescope and comparison with experimental data has been performed. The obtained results can be used for decrease of astigmatic effect on beam profile quality in design of laser systems with elements involving astigmatism.

The present work is devoted to the study of current characteristics of a high-current, plasma-filled electron gun with multi-gap initiation of explosive emission by dielectric surface flashover at different accelerating voltages and densities of plasma preliminarily filling the space between the cathode and collector. Multi-gap initiation of explosive emission is performed with the use of resistively decoupled and operating in parallel arc plasma sources which are built-in to the disk explosive-emission cathode. Plasma anode was formed by high-current reflective (Penning) discharge or by hybrid discharge matching Penning discharge with vacuum arcs. Experiments have demonstrated good emissivity of a new cathode assembly, which is approximately 1.5–2 times higher than emissivity of traditional multi-wire copper explosive-emission cathode. Stable operability of this high-current electron gun is confirmed for the amplitude of accelerating voltage in the range of 5–30 kV in contrast to mentioned above traditional gun requiring, at least, 17– 20 kV for reliable operation of the cathode.

The effect of a locally periodic magnetic field on the distribution of explosive emission erosion over the surface of a flat cathode as a result of the breakdown of the ion-matrix layer in a previously created plasma is investigated. The possibility of using the effect of a magnetic field in plasma-filled generators of low-energy high-current pulsed electron beams is estimated.

A numerical three-dimensional non-stationary model describing laser amplification process with account of the dependencies of properties of active element on temperature distribution was developed. A numerical simulation of the laser amplification process in cryogenically cooled high peak, high average power amplifier was performed and it is shown that optimization of pump parameters allows one to obtain up to 50% more energy at the output of the amplifier.

The dynamics of phase distortions during laser amplification in the cryogenically cooled active elements with high power diode pump was modeled and analyzed. The possibility of significant reduction of wavefront distortions with small decrease of the gain coefficient by choosing the optimal values of the pump radiation radius is shown.

A method for the design calculation of an electromagnet minimized by the mass of active materials, according to the dynamics, is proposed. The results of calculating the dynamic parameters of the actuating element of the circuit breakers are given: the starting time, travel time, and response time. The calculations were performed taking into account the influence on the dynamic parameters of eddy currents in the secondary circuit of the valve electromagnet. The influence on the basic dynamic parameters of such initial design data as the initial value of the working air gap, the initial mechanical force, and ambient temperature is analyzed.

The paper presents the results of studies of the operation of the inverting DC–DC converter with charge pump and LDO, which are part of the combined bipolar secondary power supply LM27762, at the near to maximum input voltage of 5.5 V and an output voltage of –4.9 V. The ripple voltages were measured at various load currents from 10 to 250 mA at the positive pole of the flying capacitor, at the output of the charge pump system and at the output of the microcircuit. It was shown for the first time on the basis of the obtained information that at low load currents up to about 107 mA the charge pump system operates in the burst mode, and at currents greater than 109 mA – in the charge pump mode with a constant frequency. The results do not confirm the information in the documentation on the microcircuit that, at themaximum input voltage of 5.5 V, the charge pump can enter the PWM mode in hot conditions. When working in burst mode, the presence of LDO in the LM27762 chip reduces the ripples of the negative voltage at the output. However, they significantly exceed the values given in the documentation on the chip. During switching to the constant–frequency mode, the level of negative voltage ripples at the output of the microcircuit decreases sharply, but it increases with further increase of the load current and exceeds the values given in the documentation.

The paper presents a project of a satellite experiment on the observation of intense flashes (transients) of electromagnetic emission from the Earth's atmosphere in different spectral ranges, as well as the measurement of medium- and long-term dynamics of spatial distribution of fluxes of energetic charged particles in the near-Earth space. To implement the experiment, it is planned to develop a Russian-Azerbaijani small spacecraft capable of carrying a payload of up to 25-30 kg. The satellite is also expected to realize a number of technology experiments, in particular, to study the effect of space flight factors on the matrices of silicon photomultipliers. We also consider the possibility of installing a telescope for photometric observations of binary stars. The requirements to the orbit and spacecraft attitude modes, as well as to its on-board systems, are considered in accordance with the goals and objectives of the experiment. The measurement data which are planned to be obtained during this experiment will subsequently be used for various scientific and applied problems including validation of existing and development of new dynamic models of radiation in the near-Earth space, ensuring the safety of the functioning of spacecraft.

The electrical properties of composite films based on conductive polymer PEDOT: PSS, graphene oxide (GO), and titanium dioxide nanoparticles (TiO2) (PEDOT: PSS– TiO2 and GO–TiO2) used as contact layers of organic and perovskite photovoltaic structures have been studied. As a result of the study of morphology by atomic force microscopy, it was found that the PEDOT: PSS–TiO2 and GO–TiO2 films have a globular structure with a grain size of ~200–300 nm. The current–voltage characteristics of the PEDOT: PSS–TiO2 and GO–TiO2 films are measured in the temperature range of 80–300 K, the dependences of the resistivity versus temperature, ρ(T), which have an activation character, are obtained. It is established that as the temperature decreases, the ρ(T) dependences show a transition from large values of the activation energy (570 meV and 329 meV) to lower values (25 meV and 2.2 meV) for the PEDOT: PSS–TiO2 and GO–TiO2 films, respectively. The mechanisms of transport of charge carriers in the materials studied are discussed.

Effect of load current and input and output capacitors on the frequency dependence of the ripple rejection ratio is studied for a classical linear voltage regulator based on an LM317L-N chip. In the absence of external capacitors, ripple rejection decreases with an increase in the load current at different input and output voltages. It is shown that a capacitor connected at the regulator output provides a significant increase in the ripple rejection ratio at frequencies of higher than 200 kHz and a capacitor connected in parallel to the regulating resistor in the feedback circuit provides an increase at frequencies of less than 300 kHz.

The Novosibirsk FEL facility has three FELs installed on the first, second, and fourth orbits of the multiturn energy recovery linac (ERL). The first FEL covers the 90–240 μm range of wavelengths at an average radiation power of 0.5 kW with a pulse repetition rate of 5.6 or 11.2 MHz and a peak power of 1 MW. The second FEL operates in the 40–80 μm range of wavelengths at an average radiation power of 0.5 kW with a pulse-repetition rate of 7.5 MHz and a peak power of around 1 MW. These two FELs are the world’s most powerful (in terms of average power) sources of coherent narrow-band (less than 1%) radiation in their wavelength ranges. The third FEL was commissioned in 2015 to cover the 5–20 μm range of wavelengths. The Novosibirsk ERL is the world’s first and only multiturn ERL. Its distinctive features include a normally-conductive 180 MHz accelerating system, a direct current (DC) electrostatic electron gun with a control grid and thermionic cathode, three operating modes of the magnetic system, and a compact (6 × 40 m) design. The Novosibirsk FEL facility has been in operation for users of terahertz radiation since 2004.

Determining the surface temperature of materials with unknown emissivity is studied. A method for determining the surface temperature using a standard sample of average spectral normal emissivity in the wavelength range of 1,65–1,80 μm and an industrially produced Metis M322 pyrometer operating in the same wavelength range. The surface temperature of studied samples of the composite material and platinum was determined experimentally from the temperature of a standard sample located on the studied surfaces. The relative error in determining the surface temperature of the studied materials, introduced by the proposed method, was calculated taking into account the temperatures of the platinum and the composite material, determined from the temperature of the standard sample located on the studied surfaces, and from the temperature of the studied surfaces in the absence of the standard sample. The relative errors thus obtained did not exceed 1,7 % for the composite material and 0,5% for the platinum at surface temperatures of about 973 K. It was also found that: the inaccuracy of a priori data on the emissivity of the standard sample in the range (–0,01; 0,01) relative to the average emissivity increases the relative error in determining the temperature of the composite material by 0,68 %, and the installation of a standard sample on the studied materials leads to temperature changes on the periphery of the surface not exceeding 0,47 % for composite material and 0,05 % for platinum.

The new NICA (Nuclotron-based Ion Collider fAсility) accelerator complex being built at the Joint Institute for Nuclear Research (Dubna, Russia) is intended for experiments with 197Au79+ gold nuclei at energies in the range of 1–4.5 GeV/n. The RF system of the collider should provide the capture of bunches to be injected from the nuclotron, the accumulation of the necessary number of particles, their acceleration (if necessary), and the formation of bunches. For this, in each ring of the collider, three types of accelerating stations are used: one barrier station and two harmonic stations. The barrier station accumulates the particles and can used to accelerate them up to the energy of the experiment. The harmonic RF stations operating at the 22th and 66th harmonics of the revolution frequency are used for the formation of bunches. This paper describes the operating modes of the RF system and the design features of the RF stations.

We demonstrate an instrument for high-precision measurements of parts manufactured with selective laser sintering systems. Operation concept is based on obtaining digital holograms of the surfaces of each layer of the part in the process of layer-by-layer sintering with subsequent processing of the obtained data and reconstruction of the internal structure and external surface of the part. Limitations of accuracy, field of view and spatial resolution are demonstrated. We demonstrate a system with less than 10 µm altitude spatial resolution with further improvement up to 1 µm. Field of view obtained is 300 mm2. Surface spatial resolution up to 100 µm is demonstrated. Compactability of system allows it to be installed in many laser sintering systems.

This paper presented a comparison of spectral properties between the phase conjugate laser with and without intracavity reflecting Bragg grating. It is shown that the Bragg grating narrows the lasing spectrum from 20.7 pm to 5.3 pm.

This paper presents a comparative analysis of technical characteristics and designs of small intermediate relays from various manufacturers. The following main characteristics of relay are considered: operation and release values; weight and dimensions; power consumption; time parameters; reliability characteristics. The design of the relays of the Russian and international manufacturers are being discussed, their design features that affect the technical characteristics are considered. It is noted that the fastening of movable contacts directly to the armature (relays from Finder, Relpol, Irkutsk Relay Plant) requires a flexible connection with the relay contacts, which leads to more complicated assembly and calibration of relays. It is shown that the kinematic diagram in the presence of free travel with no mechanical coupling with the contact pusher, used in the relay from Schrack, can reduce power consumption and increase the vibration and shock resistance of the relay break contacts. In Schrack AC relays, the operating clearance zone is configured to create a short-circuited loop with reduced electrical resistance and to provide optimum conditions for reducing armature vibration. The appropriate relay designs in terms of improving technical characteristics are proposed. The advantage of a flat return spring over cylindrical coil springs in terms of manufacturing technology and stability of mechanical characteristics of relay is shown. It was revealed that the electromagnetic drive of the Schrack relay compares favorably with electromagnetic drives of other companies in terms of the use of stray magnetic fluxes to create a useful electromagnetic torque. Based on the results of the comparative analysis and experimental study of existing relay designs, recommendations were formulated for the development of a new series of the Russian small intermediate relays within the framework of the import substitution program.

Reducing the weight of the materials used in the creation of electromagnetic devices and decreasing the overall size of the latter greatly increases the attractiveness of low-voltage switchgear such as relays, contactors, and motor starters. These goals can be achieved by forced control of their driving electromagnets and the development of a technique for minimizing weight and size. In this paper, these problems are solved for a shell-type plunger constant-voltage electromagnet used as a drive. For the preferred region of the factor space of the source design data, a computational experiment was performed in accordance with a second-order orthogonal central composite design for eight variables. The polynomial models were developed for an optimal relative proportionality of a working air gap, the winding height and thickness, the outer collar height in fractions of an optimal core diameter, and the stop height in winding fractions. Examples of the calculation of the optimal electromagnet size minimizing its overall volumetric dimensions are given.

The study of cosmic gamma ray bursts (GRBs) is one of the main goals of the Lomonosov space mission. The main advantage of this mission is simultaneous multiwavelength observations of GRBs covering the optical, X-ray and gamma-ray ranges. The mission payload includes the GRB monitor BDRG, wide-field optical cameras SHOK, and the UFFO instrument. Data are recorded mainly by the event trigger provided by the BDRG instrument, which measures the spectral and temporal properties of the burst in the energy range 10–3000 keV. The BDRG instrument also provides estimation of the source coordinates by comparing the readings of three differently directed detectors with an accuracy of several degrees. Wide-field SHOK optical cameras have a field of view of ~20° × 40°. They fix a set of images with a frequency of about five frames per second prior to the trigger and another set immediately after the trigger. The UFFO instrument includes the UBAT telescope with a coded mask for measurements in hard X-ray and soft gamma-ray ranges and an optical telescope with a slewing mirror (SMT) that can be directed on the GRB source for a time ~1 s for measuring GRB prompt emission in the early stages. In response to an BDRG trigger signal, the real-time data on a detected GRB are transmitted to the Earth via Globalstar network to the Gamma-ray Coordinates Network (GCN) and ground-based observatories. During observations on the Lomonosov satellite, 20 gamma-ray bursts were detected and catalogued. Several gamma-ray bursts were also detected in the Vernov satellite experiment. An example of such an event is given., Financial support for this work was provided by the Ministry of Education and Science of the Russian Federation, project no RFMEFI60717X0175.

A fractal-percolation system that includes extended defects and random fluctuations in the alloy composition is formed during the growth of device structures based on Group-III nitrides. It is established that the specific features of this system are determined not only by the growth conditions. It is shown that the diversity of the electrical and optical properties of InGaN/GaN LEDs (light-emitting diodes) emitting at wavelengths of 450–460 and 519–530 nm, as well as that of the electrical properties of AlGaN/GaN HEMT (high-electron-mobility transistor) structures, is due to modification of the properties of the fractal-percolation system both during the growth process and under the action of the injection current and irradiation. The influence exerted by these specific features on the service life of light-emitting devices and on the reliability of AlGaN/GaN HEMT structures is discussed.

The scientific instruments onboard the Lomonosov satellite include a complete set of detectors designed to study the gamma and optical emission of cosmic gamma-ray bursts (GRBs). The BDRG gamma spectrometer ensures producing a trigger of a GRB and studying GRB properties in the energy range of 10–3000 keV as well as determining the GRB source coordinates by comparing readings of three differently directed detectors. The SHOK optical cameras (with a field of view of ~20 × 40 degrees) fix a set of images by the GRB trigger preceding the trigger and a post-trigger set at a frequency of about five frames per second. The UFFO instrument incorporates the UBAT telescope with a coding mask for measurements within a range of hard X rays and soft gamma rays and the SMT optical slewing mirror telescope, which can be directed at the GRB source in about 1 s to measure the GRB optical emission at early stages.

Methods to accelerate transient processes in frequency spectrum synthesizers based on the pulse phase-locked loop are considered. Methods to accelerate the output voltage of the loop filter unit when using the equivalent capacitance multiplication of the capacitor methods based on the circuits with an additional current source in the charge pump current source (CPCS) unit are proposed. Diagrams of transient processes for the automatic control of the output frequency are presented. The diagrams confirm that using the proposed decisions for control by an additional current source of the CPCS unit makes it possible to approximate the transition process to the optimal value of the response speed.

Field-effect transistor (FET) structures based on soluble organometallic perovskites, CH3NH3PbBr3, were obtained and their electrical properties were studied. FETs made of CH3NH3PbBr3 films possess current- voltage characteristics (IVs) typical for ambipolar FETs with saturation regime. The transfer characteristics of FETs based on CH3NH3PbBr3 have an insignificant hysteresis and slightly depend on voltage at the source-drain. Mobilities of charge carriers (holes) calculated from IVs of FETs based on CH3NH3PbBr3 at 300 K in saturation and weak field regimes were ~5 and ~2 cm2/V s, respectively, whereas electron mobility is ~3 cm2/V s, which exceeds the mobility value ~1 cm2/V s obtained earlier for FETs based on CH3NH3PbI3.

The use of RF buckets for ion storage in the NICA is discussed. After storage, the RF2 system bunches the beam at the 22nd harmonic. Under cooling and an adiabatic increase in the RF2 voltage, a bunch shortens to the point when it fits into the separatrix of the 66th harmonic. The bunch is then recaptured into the separatrix of the 66th harmonic of the RF3 system. Ion bunches with the needed experimental parameters are formed under further cooling and an adiabatic increase in the RF3 voltage. Parasitic collisions occur at the interaction point in the process of ion storage and bunching.

The influence of optical centers concentration profiles on thermal fields under high-power end-face diode pumping is analyzed using numerical model. It is shown that non-uniform distribution profiles of optical centers concentration are very promising for high average pump power laser amplifiers. The possibility of creating concentration profiles of optical centers in gradient-activated crystals with YAG matrix with a specified distribution along the growth axis of the crystal is demonstrated. A technology of growing gradient-activated single crystal involving active mirror as active element is proposed and discussed.

We demonstrate electro-optic Q-switched solid state laser with Cr:LiSAF active medium. A single 50 ns pulse with 14 mJ of output energy is demonstrated. Simultaneous generation of several peaks with a step of 1.4 nm within the spectrum envelope with a full width at half maximum of 10.3 nm is demonstrated. For an electro-optic Q-switched mode a Pockels cell is used. Demonstrated laser can be used in differential absorption lidar systems.

We have performed a numerical simulation of picosecond pulse propagation in a combined stretcher consisting of a segment of a telecommunication fibre and diffraction holographic gratings. The process of supercontinuum generation in a nonlinear photonic-crystal fibre pumped by picosecond pulses is simulated by solving numerically the generalised nonlinear Schrodinger equation; spectral and temporal pulse parameters are determined. Experimental data are in good agreement with simulation results. The obtained results are used to design a high-power femtosecond laser system with a pulse repetition rate of .

Small-signal gain coefficient up to 1.2 per pass through active element is obtained experimentally in the laser multidisk amplifier of diode pumped solid state high peak and high average power laser system. The focal lengths of the thermal lenses are experimentally evaluated. Wavefront profiles are experimentally measured.

Temperature distribution in cryogenic cooled diode-pumped Yb:YAG crystal of multidisks high power laser system has been numerically calculated. Experimental investigation of dioptric power of the thermal lens and wavefront distortions by use of Shack-Hartman sensor has been performed. The obtained results are used for optimization of output beam parameters of pump channel of high intensity femtosecond laser system.