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The diffusion behavior of Mg in Mg/N co-implanted GaN is investigated in response to a set of annealing conditions and methodologies, namely, 1000 °C/30 min thermal anneal, by high-temperature pulsed gyrotron microwave annealing at 1420 or 1500 °C, or by thermal and microwave annealing, sequentially. After 1000 °C annealing, the diffusion of Mg in GaN is found to be negligible, as measured by secondary ion mass spectrometry. Annealing by gyrotron microwave annealing alone induces the diffusion of Mg at a rate on the order of 10−12 cm2/s. However, the use of a thermal anneal before microwave gyrotron annealing reduces this rate by an order of magnitude to 10−13 cm2/s. We find that a model that considers Mg diffusion from an inhomogeneous medium that contains a defect-rich implanted region near-surface to a relatively pristine region below the implant range better explains the observed diffusion behavior than a conventional model that assumes a homogeneous medium. By analyzing the diffusion behavior using the Boltzmann–Matano method, we present a discussion of reduction in [VGa] by thermal annealing at 1000 °C, leading to a suppressed diffusion coefficient during subsequent high-temperature annealing relative to diffusion after 1420/1500 °C annealing alone. This effect holds potential for improvement in the precision of selectively doped regions for future applications based on the (Al)GaN material system. An improved field profile control in real devices can increase the breakdown and current-handling capabilities in power electronic applications.

Vavilov-Cherenkov emission and transition radiation are the well-known phenomena and find a broad application for different scientific communities. In the case of simultaneous generation of both types of radiation, there is a possibility of interference between radiation fields. Thus, the emitted radiation could possess both transition radiation and Vavilov-Cherenkov radiation properties, that is why it should be considered as hybrid radiation. In this paper, we present the results of the theoretical investigation of X-ray hybrid radiation. Using the polarization current approach and the atomic scattering factor formalism to account anomalous dispersion of the complex permittivity we study spectral-angular distributions and polarization states of X-ray hybrid radiation when a charge obliquely falls on a foil. The theoretical results greatly contribute to understanding of X-ray Vavilov-Cherenkov radiation as well as the development of the X-ray narrow band radiation sources based on Vavilov-Cherenkov effect.

The paper states urgency of the problem of determining stress-strain state of metals of the cladding layer and the main strip in production of three-layer bimetal: alloyed steel-constructional steel-alloyed steel. Temperature field of the main strip and cladding layer is given to calculate stress-strain state of metals of three-layer bimetallic strip. Initial data for calculating this stress-strain state are given. To assess the effect of coefficient of friction between cladding layers and the main strip on stress-strain state of metals in deformation zone, three values of it are taken. Geometric model is described for calculating stress-strain state and metal flow in deformation center of cladding layer. Characteristic lines and points of calculation are provided. Technique for solving the problem of determining stresses and flows in deformation focus is described by finite element method using ANSYS app. Regularities of flow of cladding layer’s metal along the length of deformation center and movement of the main strip of bimetallic ingot are given. Values of mutual displacement of layers of bimetallic strip are determined as a function of deformation degree of the cladding layer. And the recommendations are given on this degree to improve quality of a three-layer bimetal. Regularities of distribution of axial and tangential stresses in deformation center are presented for production of steel three-layer bimetallic strips in the unit of combined continuous casting and deformation. Stress state of the cladding layer’s metal in focus of cyclic deformation was estimated from the position of improving quality of three-layer bimetallic strips produced in such unit. © 2019 National University of Science and Technology MISIS. All rights reserved.

Relativistic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms for >1 MeV electron flux depletion in the Earth's radiation belts. Resonant electron interaction with EMIC waves is traditionally described by quasi-linear diffusion equations, although spacecraft observations often report EMIC waves with intensities sufficiently large to trigger nonlinear resonant interaction with electrons. An important consequence of such nonlinear interaction is the resonance broadening effect due to high wave amplitudes. In this study, we quantify this resonance broadening effect in electron pitch-angle diffusion rates. We show that resonance broadening can significantly increase the pitch-angle range of EMIC-scattered electrons. This increase is especially important for [Formula: see text] MeV electrons, where, without the resonance broadening, only those near the loss cone (with low fluxes) can resonate with EMIC waves.

The effect of long-wavelength magnetic field disturbances typical of the Earth’s auroral region on the generation of auroral kilometric radiation in a narrow three-dimensional plasma cavity in which a weakly relativistic electron flow propagates against the background of cold low-density plasma is analyzed. The dynamics of the propagation and amplification of fluctuation waves with initial group velocities directed toward the higher magnetic field is considered in the geometrical optics approximation. Analysis of wave trajectories shows that the wave amplification coefficients depend on the magnetic field gradient in the reflection region. If the wave reflection point lies in the region where the gradient of the disturbed magnetic field is less than that of the undisturbed dipole field, then the wave amplification coefficients exceed those of waves propagating in the undisturbed field, and vice versa. Thus, the shape of the spectrum of generated waves changes in the presence of long-wavelength disturbances of the dipole magnetic field in such a way that segments with different curvatures can form in the spectrum.

The first observation and investigation of a new mechanism of resonant Cherenkov diffraction radiation appearing when relativistic 6 MeV electrons move alongside a periodically shaped Teflon target have been presented and analysed. Numerical simulations performed using computer code KARAT are in good agreement with the experimental results. This new mechanism is a promising technique for generation and monochromatisation of THz and sub-THz radiation beams that could be integrated into any short bunch linear accelerator facility including 4th generation light sources providing new opportunities for user community.

The main loads acting on the backup-walls of the assembled mold of the combined continuous casting and deformation unit in production of steel sheets for welded pipes are described. The technique for determining the total stresses in backup-walls of the installation of the compression forces and the temperature load is given. The temperature boundary conditions for determining the temperature fields in the backup-walls of the assembled mold of the unit for steel sheets for welded pipes production are depicted. The dependence for determining the heat flux density of the deformation center hot metal influencing working surface of the backup-wall during workpiece drafting is considered, as well as the technique for determining values of effective heat transfer coefficients for backup-walls cooling by water. The procedure for determining temperature fields and thermoelastic stresses on backup-walls of the installation is described using the ANSYS package. The article considers the initial data for determining temperature fields and thermoelastic stresses in backup-walls of the assembled casting mold of the installation. The results of temperature fields and thermoelastic stresses calculation are achieved in five sections of the backup-wall and are provided for the typical lines. The nature of temperature distribution along the backup-wall thickness during cooling by water at idle and at contact with the workpiece during its compression is shown. For the calculated temperature fields, axial and equivalent stresses, that arise in the backup-walls without channels when the workpiece is drafted and cooled with water at idle, are determined. The values and regularities of distribution of axial and equivalent stresses along the thickness of the contact layer and along the height and thickness of the backup-walls during drafting of the workpiece and at idle are presented. The values and regularities of the distribution of total axial stresses along the thickness of the contact layer, the height and thickness of the backup-walls from the drafting forces and the temperature load are given. © 2018, National University of Science and Technology MISIS. All rights reserved.

The prospects of development of combined continuous casting and deformation processes in production of steel sheets for welded pipes are considered. Design of a pilot plant for combined continuous casting and deformation process for production of steel strips is described. Technological possibilities of installation of combined continuous casting and deformation process are described from the point of improving the quality of steel sheets for welded pipes as well as operating conditions of comb mold backup-walls of combined casting and deformation plant in production of them. Problem of simultaneous determination of stress-strain state of metal with focus on cyclic deformation and stress is posed, depending on compression force in walls of the comb molds of the installation. Initial data and boundary conditions for determination of stress-strain state of metal in focus of cyclic deformation are given using the ANSYS package. Diagrams of axial stresses are presented for preparation of sheets with section of 3×2250 mm made of 09G2S steel. Evaluation of the scheme of stressed state of metal with focus on cyclic deformation from the position of high-quality steel sheets production for welded pipes was carried out. Technique of determination of axial stresses is described depending on compression forces in steel sheets production for welded pipes in continuous casting and deformation plant. Design scheme and loading pattern of the backup-wall are given. Stress state of the backupwall is calculated in five sections, the results are presented for typical lines. The values and regularities of distribution of axial stresses in contact layer, in height and width of the backup-wall were determined depending on compression forces. Values of the greatest compressive and tensile stresses are given in relation to compression forces and their distribution in the backup-walls during production of steel sheets for welded pipes in combined continuous casting and deformation plant. © 2018, National University of Science and Technology MISIS. All rights reserved.

Co-implantation of Mg with N has been shown to improve p-type conductivity in Mg-implanted GaN. Achievement of p-type material still requires temperatures beyond the thermodynamic stability of GaN, however. In this study, we present results of implantation and anneal activation of GaN, co-implanted with Mg and N or Mg only by repeated, short thermal cycles of 1350 °C using a high-power gyrotron microwave source with a quasi-gaussian intensity profile. Spatial variations in optical and electrical properties of the resulting films are characterized by photoluminescence and diode I–V and C–V measurements. Resistive Mg/N co-implanted and annealed material shows dominant luminescence of the VN-related green luminescence (GL2) band at 2.37 eV and relatively lower intensity acceptor-related ultraviolet luminescence (UVL) at 3.27 eV. However, a material showing p–n diode behavior shows higher-intensity UVL luminescence and suppression of the GL2 band, permitting observation of the yellow luminescence (YL) present in the as-grown GaN. The YL is attributed to unintentionally introduced CN–ON complexes and is commonly observed in GaN grown by metalorganic chemical vapor deposition but is typically absent in implanted/annealed GaN. Co-implanted material is compared to material implanted only with Mg and annealed under the same conditions, which shows p-type activation, but contains persistent GL2 luminescence post-anneal and lowers maximum hole concentration.

This paper numerically and experimentally demonstrates the influence of the space charge forces in short electron bunches on the spectrum of coherent transition radiation. To estimate and optimize dimensions of a short electron bunches produced by the KEK LUCX RF gun, ASTRA software was employed. Obtained results indicate that the modification of the femtosecond UV laser pulse transverse profile allows to decrease the space charge forces. The simulation results were confirmed experimentally with the good agreement.

Grating transition radiation (GTR) emitted by electrons interacting with a diffraction grating was experimentally confirmed. This radiation appears when a charge intersects the grating at some inclination angle θ between the main grating plane and the charge velocity vector. If the condition θ = 0 is fulfilled the GTR tends to the conventional Smith-Purcell radiation. In this report we present the experimental investigation of spectral and orientation dependencies of a coherent GTR in sub-THz wavelength region emitted by 8 MeV electron at KEK LUCX facility. The coherent GTR spectral line shapes up to 5th diffraction order were measured for different inclination angles (θ = 0–25 deg) with the grating period 4 mm. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands 60–90 GHz and 320–460 GHz were used. The estimation of radiation frequency dependence on the inclination angle using the dispersion relation justifies the usage of different narrow-band SBD detectors to investigate different diffraction orders of coherent GTR spectral lines. It was shown that the bandwidth of the GTR spectral lines decreases with the diffraction order. The comparison with coherent transition radiation in the same frequency range showed that the brightness of both radiation mechanisms are comparable.

On the basis of comparison of the influence of the stock exchange factors on the pricing of nonferrous metals for medium term with similar results for short term, it has been established that the main attention should be paid to the changes in the pricing environment on the metal market as a function of the prices of exchange traded metals. The situation on the market of energy carriers (hydrocarbons) and the European, American, and Asian stock exchanges can be based on parity and even significantly influence the variation of the metal prices. In the medium term, constructive development of metal trade should be reasonably promoted by changing the elasticity of supply with regard to prices for exchange traded metals and by applying the stock exchange factors that positively influence the pricing on commodity and stock markets.

Introducing systems capable of profound reduction in a casting and rolling module improves the product quality, on account of the intense working of large continuous-cast slabs over the whole cross section and the production of uniform fine-grain structure of the metal, and also increases the cross section of continuous- cast billet. Analysis of the formation of nonmetallic inclusions and segregation in the axial zone of the thick rolled sheet is followed by analysis of the nonuniform deformation over the slag height in the reduction of large continuous-cast slabs at the 5000 mill at OAO Magnitogorskii Metallurgicheskii Kombinat. The structure of a cyclic-deformation system for preliminary deformation of large continuous-cast slabs is described, and its capabilities are explored. Hammers for preliminary deformation of large continuous-cast slabs are considered. Experimental data are presented for the deformation of continuous-cast steel 45 and 12Kh18N10T steel billet. The structure of the continuous-cast billet is assessed in the course of reduction on the cyclic-deformation system. The basic parameters of the system for preliminary deformation of large continuous- cast slabs are determined. The capabilities of the cyclic-deformation system are outlined in terms of increase in sheet quality. On that basis, the use of the cyclic-deformation system in the continuous-casting line for preliminary reduction of large continuous-cast slabs is recommended: it permits matching of the speed of continuous-casting and cyclic-deformation processes; and ensures 45–90% reduction in a single pass so as to obtain well-worked cast structure over the whole slab cross section. When using the cyclic-deformation system in the continuous-casting line, the continuous-cast slabs are reduced by means of the heat of the cast metal, thereby greatly reducing the energy consumption in billet production. The cyclic-deformation system may be used with thick-sheet and broad-strip mills for preliminary single-pass reduction of the hot slab, with improvement in sheet quality and reduction in the number of passes in the mills. © 2017, Allerton Press, Inc.

The Cherenkov effect is a well-known phenomenon and its properties are widely used in many fields of physics. However, some features of the polarization characteristics of Cherenkov radiation that appears when charged particles pass near azimuthally asymmetric, finite dielectric targets are still poorly studied. This problem is solved in this work. The polarization characteristics of Cherenkov radiation in the case of a rectangular dielectric screen are analyzed using the Stokes approach. Owing to the azimuthal asymmetry of the target, radiation acquires an elliptic polarization whose rotation direction and inclination angle depend both on the direction of radiation propagation and on the dielectric properties of a substance. The results demonstrate that the Cherenkov effect can be used to create sources of elliptically polarized radiation with the controlled direction of polarization rotation.

The generation of auroral kilometric radiation in a narrow 3D plasma cavity, in which a weakly relativistic electron flow is propagated along the magnetic field against a low-density cold background plasma, is studied. The time dynamics of the propagation and intensification of waves are analyzed using geometric optics equations. The waves have different wave vector components and start from the cavity center at an altitude of about the Earth’s radius at plasma parameters typical for the auroral zone at this altitude. It is shown that the global inhomogeneity of the Earth’s magnetic field is of key importance in shaping the auroral kilometric radiation spectra.

The open trade on the world market is estimated using information of one-day exchange prices of nonferrous and precious metals, oil, reduced crude, and gasoline and the main world stock indices in the time period from January 1, 2009 to December 31, 2015. It is found that the short-term changes in the prices of nonferrous metals are determined by the prices on the metal market. The changes in the prices of energy carriers and the stock trade on the stock market weakly influence the pricing of nonferrous and precious metals. The prices of metals depend on the situation during trade on commodity exchanges, and the stock market indirectly influences the exchange prices of metals through changes in the share prices of the companies that produce copper, aluminum, and zinc.

Transition radiation appearing when a charged particle crosses the interface between two media with different dielectric constants, e.g., a metal–vacuum interface, has been well studied in a wide spectral range. However, primarily, radiation from smooth interfaces has been studied. Transition radiation from conducting gratings (grating transition radiation) is experimentally studied and theoretically analyzed in this work. In this case, it is possible to obtain monochromatic radiation with a tunable frequency depending on the rotation angle of the grating with respect to the electron momentum. Coherent grating transition radiation can be efficiently used as a source of terahertz radiation based on the use of a compact electron accelerator with an energy below 10 MeV and a bunch duration of ≤1 ps.

Here we present for the first time the use of gyrotron beam for selective annealing/activation of implanted Mg in bulk GaN films. Samples with 1 μm uGaN epi-Iayer grown by MOCVD on HVPE bulk n+GaN substrates were implanted with Mg (1 x 1019 cm−3) to a target depth of 500 nm. A systematic investigation of annealing temperature, N 2 overpressure, surface capping layer, and sample orientation to the beam are presented. Post-implantation, volumetric lattice deformation was recovered by performing continuous annealing at temperatures $>$ 1100 °C for 30 s. Both AIN capped and uncapped samples were studied. It is shown that the surface of uncapped GaN samples which were annealed at 1100 °C in 40 bar N 2 overpressure remained intact. Photoluminescence spectroscopy was performed and confirmed the incorporation of Mg in substitutional sites with this technique, along with formation of large density of nitrogen vacancy defects.

The main objective of the project is to build a high resolution time-profile monitor for femtosecond electron beams, based on the spectral analysis of coherent Smith-Purcell radiation (cSPr). The monitor will be capable of determining the electron bunch time profile non-destructively and on a shot-by-shot basis. The results of recent experimental and theoretical studies are presented, and the conceptual design of the monitor is discussed.

A key step to the development of future (Al)GaN-based power devices is the ability to form selective-area p-type regions, and a promising method of accomplishing this is through ion implantation of the dominant acceptor dopant, Mg. Ion implantation in GaN induces lattice damage and creates point defects, including vacancies and interstitials. To remove this damage, heal defects, and activate the implanted dopants requires temperatures >1000 °C, beyond the thermodynamic equilibrium stability of GaN [1]. Removal of point defects, especially donor-like nitrogen vacancies (VN) in the material can be accomplished through high temperature annealing and may be aided by co-implantation with N [2]. It is speculated that compensation of implant-induced VN may be enhanced during the annealing process by diffusion of implanted Ni to the corresponding site in the N sublattice, however evidence for such compensation through suppression of VN-related photoluminescence has not been reported in p-type material. Methods of high-temperature nonequilibrium annealing such as symmetric multicycle rapid thermal annealing (SMRTA), microwave annealing, and laser annealing have been reported to achieve p-type material, however activation of Mg-implanted material remains an area of active study. In this study, we report our latest results in obtaining p-type conductivity in implanted GaN by repeated, short-duration thermal cycles using a high-power (kW) gyrotron microwave source and systematic study of Mg implantation and Mg+N co-implantation into GaN and the resulting defect microstructure [3]. We examine the effect of co-implantation to depths of 250 nm and 500 nm, and Mg:N concentration ratios of 1 and 2 with [Mg]=1019 cm-3. Implanted MOCVD-grown u-GaN is capped with AlN and annealed for 2 overpressure of 3 MPa. The optical and electrical properties of the resulting films are characterized by temperature-dependent photoluminescence (PL) and I-V measurements of vertical p-i-n diodes. Highly resistive Mg+N co-implanted and annealed material shows dominant luminescence of the VN-related GL2 band at 2.37 eV and relatively lower-intensity acceptor-related UVL and UVL* bands (at 3.05–3.27 eV). However, implanted/annealed samples showing p-n diode behavior (Vth=3–3.1 V at room temperature) and hole concentrations in the range of 1015–1017 cm-3 show dominant/high UVL/UVL* bands and YL band centered at 2.30 eV. The YL is attributed to unintentionally introduced CN-ON complexes and is commonly observed in GaN grown by MOCVD but is typically not observed in implanted/annealed GaN. Additionally, samples implanted only with Mg and activated under the same annealing conditions show persistent dominance of the GL2 band in this range. This work is funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy under the PNDIODES programs directed by Dr. Isik Kizilyalli. [1] G. Alfieri, et al. J. Appl. Phys., 123, 205303 (2018) [2] R. Tanaka et al. Japan. J. Appl. Phys., 59 , SGGD02 (2020) [3] V. Meyers et al. manuscript submitted for publication (May 2020) Figure 1

Generation, amplification, and propagation of auroral kilometric radiation in a narrow three-dimensional plasma cavity in which a weakly relativistic electron beam propagates is studied in the geometrical optics approximation. It is shown that the waves that start with a group velocity directed earthward and have optimal relation between the wave vector components determining the linear growth rate and the wave residence time inside the amplification region undergo the largest amplification. Taking into account the longitudinal velocity of fast electrons results in the shift of the instability domain toward wave vectors directed to the Earth and leads to a change in the dispersion relation, due to which favorable conditions are created for the generation of waves with frequencies above the cutoff frequency for the cold background plasma at the wave generation altitude. The amplification factor for these waves is lower than for waves that have the same wave vectors but are excited by the electron beams with lower velocities along the magnetic field. For waves excited at frequencies below the cutoff frequency of the background plasma at the generation altitude, the amplification factor increases with increasing longitudinal electron velocity, because these waves reside for a longer time in the amplification region.

The laws of formation of price clusters are revealed upon statistical processing of the data on changing the quotation prices of nonferrous and precious metals, oil, black oil, gasoline, and natural gas in the postcrisis period from January 1, 2009 to November 1, 2013. It is found that the metal prices entering in the price cluster of nonferrous metals most strongly affect the formation of the nonferrous metal price and that the prices of precious metals and energy carriers correct the exchange price of the metal to some extent but do not determine its formation. Equations are derived to calculate the prices. The results of calculation by these equations agree well with the real nonferrous metal prices in the near future.

We demonstrate p-type activation of GaN doped by Mg ion implantation, and in situ during metalorganic chemical vapor deposition through sequential short-duration gyrotron microwave heating cycles at temperatures of 1200–1350 °C. GaN is implanted with 1019 cm−3 Mg ions, capped with AlN, and annealed under 3 MPa N2 overpressure in 5 s heating cycles for less than 60 s total using a high-power gyrotron microwave heating source. Through I–V characterization, photoluminescence spectroscopy, and Raman spectroscopy, we study the evolution of electrical properties, optically active point defects, and material strain in response to implantation and annealing. For Mg-implanted samples, increasing annealing temperature is characterized by an increase in the PL substitutional Mg-related peak (UVL) relative to the shallow-donor vacancy-related peak (GL2). Through comparison of implanted and in situ doped samples, it is demonstrated that the origin of compensating VN lies primarily in implantation rather than degradation from the annealing process. Transmission line measurements and diode I–V measurements show a sheet resistance of 1083 kΩ/□ and a hole concentration of 1.23 × 1015 cm−3, respectively, in the Mg-implanted material annealed at 1350 °C. We conclude that temperature-cycled gyrotron annealing at 1350 °C decreases implant-induced compensating point defects and activates Mg to obtain selective p-type conduction.

Micro-bunched particle beams are used for a wide range of research including tunable sources of THz radiation. In most of the applications accurate and non-destructive monitoring of the bunch-to-bunch separation is required. We present the results of proof-of-principle experiments on measuring the distance between two micro-bunches via the analysis of the coherent Smith-Purcell signal amplitude modulation. The proposed monitor can be used to provide feedback to control the sum-millimeter distances between the femtosecond long micro-bunches to stabilize the operation of a THz oscillator or to position the witness bunch into the right phase of the wakefield.

Quasi-monochromatic X-rays with high brightness have a broad range of applications in fields such as life sciences, bio-, medical applications, and microlithography. One method for generating such X-rays is via inverse Compton scattering (ICS). X-ray generation experiments using ICS were carried out at the superconducting RF test facility (STF) accelerator at KEK. A new beam line, newly developed four-mirror optical cavity system, and new X-ray detector system were prepared for experiments downstream section of the STF electron accelerator. Amplified pulsed photons were accumulated into a four-mirror optical cavity and collided with an incoming 40 MeV electron beam. The generated X-rays were detected using a microchannel plate (MCP) detector for X-ray yield measurements and a new silicon-on-insulator (SOI) detector system for energy measurements. The detected X-ray yield by the MCP detector was 1756.8±272.2 photons/(244 electron bunches). To extrapolate this result to 1 ms train length under 5 Hz operations, 4.60×10 5 photons/1%-bandwidth were obtained. The peak X-ray energy, which was confirmed by the SOI detector, was 29 keV, and this is consistent with ICS X-rays.

This paper demonstrates the detailed design concept, alignment, and initial testing of a Michelson interferometer for the THz spectral range. We present the first results on the measurement of a coherent transition radiation spectrum and describe the performance of a pair of ultra-fast broadband room temperature Schottky barrier diode detectors. We discuss the main criteria of interferometer beam splitter optimization, the alignment technique, the high-precision calibration and linearity check of the motion system.

In this report we present experimental investigations of THz radiation generated from a corrugated and a non-corrugated capillary with reflectors, using a femtosecond electron beam of LUCX accelerator at KEK, Japan. We discuss measurements of radiation angular distributions and their comparison with Particle In Cell simulations, and also investigate an off-central propagation of the beam in the capillaries based on experimental measurements and simulations., Comment: 5 pages, 5 figures

Investigation of coherent Smith-Purcell Radiation (SPR) spectral characteristics was performed both experimentally and by numerical simulation. The measurement of SPR spectral line shapes of different diffraction orders was carried out at KEK LUCX facility. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands of $60-90$~GHz and $320-460$~GHz was used in the measurements. Reasonable agreement of experimental results and simulations performed with CST Studio Suite justifies the use of different narrow-band SBD detectors to investigate different SPR diffraction orders. It was shown that monochromaticity of the SPR spectral lines increases with diffraction order. The comparison of coherent transition radiation and coherent SPR intensities in sub-THz frequency range showed that the brightnesses of both radiation mechanisms were comparable. A fine tuning feasibility of the SPR spectral lines is discussed., Comment: 7 pages, 7 figures, 3 tables

The nonlinear stage of Kelvin-Helmholtz (KH) instability in a finite-width plane-parallel plasma flow is analyzed. The analysis is performed by means of two-dimensional numerical simulations with the use of ideal magnetohydrodynamic equations describing isothermal plasma flows propagating along the magnetic field. The influence of the magnetic field strength, the plasma temperature, and the ratio of the flow width to the width of the transition layer on the formation of vortex layers and large-scale flow perturbations is investigated. It is shown that, if the wavelength of periodic perturbations is shorter than the flow width, the symmetric and antisymmetric modes develop in a qualitatively similar manner. For waves with wavelengths longer than the flow width, the development of such modes is very different due to the mutual influence of the flow boundaries. Analysis of the development of instability at different values of the Alfven Mach number M A shows that long-lived vortices with a characteristic scale length on the order of the flow width appear in a weak magnetic field for both symmetric and antisymmetric modes; however, the vortex geometries for these modes are different. In a strong magnetic field, M A ∼ 5, the phase of vortex decay for both types of modes occurs faster than in a weak field; however, in the case of an antisymmetric mode, large-scale perturbations of the flow boundary are retained for a longer time. Analysis of the evolution of the initial disturbance produced by an ensemble of random small perturbations (noise) at different plasma temperatures shows that, for a flow width comparable with the width of the transition region, the development of KH instability is always antisymmetric in character and leads to well-developed large-scale perturbations of the flow as a whole. For a cold plasma with C S < 0.5U (where C S is the speed of sound and U is the flow velocity), in contrast to hot plasma with C S > 0.5U, the development of KH instability leads to the growth of the antisymmetric mode even if the flow width is much larger than the width of the transition region.

The function of endothelium of microcirculation vessels, vegetative and psychoemotional status, lipid spectrum and physical efficiency in 43 young sportsmen are corrected with the aid of Tentorium api-phyto products (APP). The following tests were conducted: samples of reactive hyperemia and hyperventilation, ultrasound investigation of brachial artery, determination of performance efficiency, total cholesterin, triglycerides, cortisol, red cells, vegetative and psychoemotional status by the Spielberger’s test and SAN test, as well as biomicroscopy of sclera. To relief the psychophysical stress, improve the endothelium function and performance efficiency, the sportsmen received APP as a food additive. After the reception of APP, the lipid and cortisol levels decreased markedly, and the level of red cells increased. The aerobic capacity increased. The recovery time after exercise shortened. The vegetative stress level decreased significantly, and the psychoemotional status improved. The endothelium dysfunction removed. It is shown that APP is a new method of prophylaxis of sudden death in sport, in people with blood circulation pathology, creative professionals, and businessmen.

This paper demonstrates the application of a polarization current approach to estimate the yield of soft x-ray Cherenkov radiation when a charged particle travels in the vicinity of a finite-size screen. To account for resonant anomalous dispersion of the complex permittivity, we apply the formalism for the atomic scattering factor. We derived the simple analytical expression for the radiation field, which allows us to determine all properties for a wide energy range of emitted radiation of a charged particle. The influence of screen sizes on Cherenkov radiation characteristics is determined by macroscopic and microscopic approaches.

As is generally known, the integral of the electric field strength over all time for usual (bipolar) radiation is zero. The first demonstration of the possibility of unipolar radiation generation has been considered theoretically by Bessonov in 1981 [E.G. Bessonov, Zh. Eksp. Teor. Fiz. 80 (1981) 852]. According to this work, the unipolar radiation (or strange electromagnetic waves) is radiation for which the integral of the electric field strength over the entire duration of a pulse differs significantly from zero. Later, several theoretical papers devoted to this phenomenon have appeared in the literature, where authors investigated mainly synchrotron radiation. However, despite the critical interest, the experimental investigations ignored this effect. In this paper we present results of the first experimental investigation of the unipolar radiation generated by a relativistic electron beam. To detect the unipolar radiation the detector that is sensitive to the selected direction of the electric field strength has been elaborated and tested. We used a designed detector to observe the coherent backward diffraction radiation appearing when a bunched electron beam travels in the vicinity of a flat conductive target. The asymmetry of the electric field strength of the coherent backward diffraction radiation has been demonstrated.

The design of a compact Fabry-Pérot interferometer (FPi) and results of the experimental studies carried out using the device are presented. Our FPi uses freestanding wire-grid polarizers (WGPs) as beamsplitters and is suitable for use at terahertz (THz) frequencies. The FPi was studied at the LUCX facility, KEK, Japan, and an 8 MeV linear electron accelerator was used to generate coherent Smith-Purcell radiation. The FPi was designed to be easy to align and reposition for experiments at linear accelerator facilities. All of the components used were required to have a flat or well understood frequency response in the THz range. The performance of the FPi with WGPs was compared to that of a Michelson interferometer and the FPi is seen to perform well. The effectiveness of the beamsplitters used in the FPi is also investigated. Measurements made with the FPi using WGPs, the preferred beamsplitters, are compared to measurements made with the FPi using silicon wafers as alternative beamsplitters. The FPi performs well with both types of beamsplitter in the frequency range used (0.3-0.5 THz). The successful measurements taken with the FPi demonstrate a compact and adaptable interferometer that is capable of analyzing THz radiation over a broad frequency range. The scheme is particularly well suited for polarization studies of THz radiation produced in an accelerator environment.

Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

We propose a new method for activation of source/drain junctions by microwave annealing. A study with B/BF2 implants at ultralow energies (300/500 eV) and high doses (1E15/5E15 cm−2) was completed. The samples were subjected to a high-power cyclotron resonance maser, called a “gyrotron,” for annealing. There appears to be some evidence of electromagnetic field-aided activation. The activation levels achieved exceed the levels reported by thermal means at the corresponding temperatures. Secondary ion mass spectroscopy (SIMS) was used to examine the impurity profile after ion implantation and diffusion. Spreading resistance profiling was used to examine the activated dopant profile.

During the interaction of the relativistic electrons field with a dielectric target various types of electromagnetic radiation, such as Cerenkov radiation, diffraction radiation, transition radiation can be generated. In this report we present the results of experimental studies of the diffraction radiation generated by relativistic electrons in a dielectric target at the interface vacuum-insulator and insulator-conductor in the millimeter wavelength range. The experimental results show that the component of the diffraction radiation of relativistic electrons at the interface insulator-conductor, for any significant refractive index of insulator, is suppressed. The analysis of the results from different points of view was done.

Geometry of Vavilov-Cherekov (VChR) radiation when an electron moves close to a dielectric target is in analogy to diffraction radiation (DR) geometry. In this case we may expect DR generation from the upstream face of the target besides that VChR. The joint observation of these booth types of radiation is very interesting from the pseudo-photon viewpoint, which is applicable for relativistic electrons. Unexpected results obtained in our experiment insist on reflection about nature both DR and VChR. The experiment was performed on the relativistic electron beam of the microtron of Tomsk Polytechnic University., Comment: This article will be published in Journal of Physics

The problem of "semi-bare electron" was first considered in frame of quantum electrodynamics by E.L. Feinberg in 1980. In theory in frame of classical electrodynamics this problem was touched on in articles of N.F. Shul'ga and X. Artru. In 2008 the experimental investigations of this phenomenon in millimeter wavelength region were started by the group of scientists, including authors of this article. Used technique allowed us to study this effect in macroscopic mode. In this paper we present the results of direct observation of a semi-bare electron coulomb field recovery. The semi-bare state was obtained by passing of electron beam through the hole in a conductive screen. Measured spatial distribution of electromagnetic field shows the process of recover of the electron coulomb field, which is followed by a forward radiation. The experiments were performed on the relativistic electron beam of the microtron of Tomsk Polytechnic University., Comment: The article will published in Journal of Physics

To assess a training effect correcting endothelial dysfunction (ED), neurovegetative status and atherosclerosis risk factors (ARF) in male students.Ninety healthy students aged 18-25 years with ARF and ED were followed up after bicycle exercise (BE) 3 times a week: 30 males did BE for 1 month, 30--for 2 months and 30--for 3 months. Blood lipids, exercise tolerance (ET), parameters of cardiointervalography, dopplerangiography of the brachial artery and rheovasography of the forearm at rest and in tests with reactive hyperemia, hyperventilation were estimated immediately after, 1 and 3 months after BE.Two-month BE forms adequate structural trace the effect of which can be partially found 3 months later. Three-month BE tells on adaptation as it produces proatherogenic shifts in blood lipids. After the two-month cycle of BE positive effects regress in the following order: normalization of blood lipids, improvement of vegetovascular reactivity, high exercise tolerance and endothelium-related vasodilation.Two-month exercise is effective and safe, forms adaptive reserve of the body, structural effect of which partially persists for 3 months.

Hemodynamics of forearm and neurovegetative status were studied in 142 clinically healthy male students with risk factors of atherosclerosis and in 54 male students without risk factors of atherosclerosis at rest and during test with reactive hyperemia. Rheovasography of forearm, cardiointervalography, Doppler examination of brachial artery, and test with reactive hyperemia were undertaken in all subjects. The results testify to the fact that endothelial dysfunction leads to spastic state of regional hemodynamics and hyperactivity of sympathetic nervous system at rest as well as during reactive hyperemia which has a "delayed" character.

Optical transition radiation (OTR) arising when a relativistic charged particle crosses a boundary between two media with different optical properties is widely used as a tool for diagnostics of particle beams in modern accelerator facilities. The resolution of the beam profile monitors based on OTR depends on different effects of the optical system such as spherical and chromatic aberrations and diffraction. In this paper we present a systematic study of the different optical effects influencing the OTR beam profile monitor resolution. Obtained results have shown that such monitors can be used for sub-micrometer beam profile diagnostics. Further improvements and studies of the monitor are discussed.

Numerical simulations of Backward Transition Radiation originating from a flat ideally conducting target inclined at 45 degrees with respect to a charge propagation direction are presented in this paper. The simulation results are compared with the theory for the wave and pre-wave zones. The main characteristics of the simulated radiation distributions are discussed in detail.