The paper presents numerical results of simulations of the deposition process of a complex optical coating using broadband monitoring of this process in the case when the noise level in the measured transmittance coefficient has an uneven distribution along the wavelength. The influence on the accuracy of data control at the edges of the measured wavelength range, where the error in the transmittance coefficient is maximum, is investigated. It is shown that when a part of the data is removed at the edges of the range, the self-compensation coefficient of the deposition process errors almost does not change, while the average norm of the error vector of layer thicknesses significantly decreases. Thus, it is shown for the first time that taking into account the effect of self-compensation of errors in broadband control opens up the possibility of a reasonable choice of the optimal spectral range of optical control for practice.
Show AbstractFor the program of studying photonuclear reactions on gamma-beams of the source from backward Compton scattering under developing, when the output energy is Egamma < 40 MeV, activation experiments are proposed as initial ones, which are important both for developing methods for tuning and monitoring gamma-beams, and for studying the excitation of pygmy and giant resonances in atomic nuclei and the multiplicity of photoneutrons from the processes of deexcitation of giant resonances.
Show AbstractAn analysis of experimental and theoretical data on the study of preferential sputtering of nickel- and copper-platinum-based alloys during bombardment with an ion beam was carried out. It is shown that, in contradiction with existing models, the main factor determining the process of preferential sputtering is the ratio of the surface binding energies of the components.
Show AbstractA model for the evolution of surface nanorelief under irradiation with gas cluster ions is proposed. The model is based on consideration of individual collisions of clusters with a surface. The amount of substance sputtered from the collision area and the efficiency of its redeposition onto other surface elements are determined. The performance of the model is shown when compared with experimental data. The stages of smoothing of a harmonic relief are studied. A new measure of the effectiveness of surface smoothing is proposed.
Show AbstractAn indirect-drive cryogenic target is necessary for research in the field of laser thermonuclear fusion at a megajoule energy level facility. Solid fuel layer in the target must meet high requirements: a roughness of the inner cryolayer surface must be less than 1 µm, deviations from the sphericity and the concentricity must be less than 1%. This paper describes the results of the research on meeting these requirements, notably, cryolayer formation and its characterization. Due to the slow crystallization method of the deuterium layer with its simultaneous heating by IR radiation it is possible to obtain deviations from the sphericity and the concentricity of the inner cryolayer surface within limits of 2%, the roughness - within limits of 20 mkm. Theoretical thermal calculations of the target construction are compared with experiment. The program system was developed using the optical shadow method which makes it possible to measure liquid fuel when filling the shell during the performance of the experiment, to perform the characterization of the solid cryogenic layer parameters, to evaluate characterization results robustness.
Show AbstractThe possibilities of engineering energy losses of electrons created in the cascade process of electron-electron scattering during the interaction of multilayer dielectric structures with ionizing radiation are considered. It is shown that the contribution of surface plasmons associated with layer boundaries to electron energy losses is significant only for nanometer layer thicknesses and increases with increasing electron energy. At the same time, surface states associated with longitudinal optical phonons in ionic crystals significantly change energy losses during electron thermalization and can lead to an increase in the efficiency and growth rate of scintillation in nanostructured systems.
Show AbstractIron dichalcogenides intercalated with alkali metal atoms attract the attention of physicists due to their unusual natural phase separation, in which superconducting clusters are formed at the boundaries of the antiferromagnetic phase. In this work, using photoelectron spectroscopy technique, we discovered an unusual effect that presumably arises due to this phase separation. We studied the temperature dependences of the photoelectron spectra of Se 3d, Fe 3p and the valence band at temperatures above and below $T_c \approx 27$~К of the compound (K$_{0.8}$Na$_{0.2}$)$_{0.8}$Fe$_{1.8}$Se$_2$ with a unique substitution of alkali metal atoms. A strong temperature dependence of both the valence band and core levels was discovered: we observed a strong broadening of the spectra, which monotonically decreased with increasing sample temperature, while the temperature changes were cyclic. We believe that this broadening is associated with the appearance of space charges in the dielectric matrix, which leads to band bending. Moreover, the shape of the potential arising inside a given compound was reconstructed, and an estimate was obtained for the relative amounts of dielectric and superconducting phases. The results obtained will help to better understand the physical processes occurring in this compound.
Show AbstractThe previously proposed method of molecular dynamics simulation of the deposition of thin films from metal targets is adapted to the case of dielectric targets and applied to silicon dioxide films. The possibility of not only silicon atoms leaving the target, but also clusters with oxygen atoms was taken into account by adding O=Si=O molecules to the flow of deposited atoms. Atomistic film clusters were obtained by high-energy and low-energy deposition at different percentages of molecules in the flow of deposited atoms. The values of the stress tensor components are calculated. With high-energy deposition, compressive stresses are observed, with low-energy deposition, tensile stresses are observed. The absolute values of the diagonal components of the stress tensor increase with increasing proportion of molecules in the flow of deposited atoms.
Show AbstractAlloys studied in this work are of interest for the needs of hydrogen energy, electronics, pharmacology. The aim of the research is to reveal regularities of defect subsystems development, which is necessary for development of processes to improve performance of metallic systems. Probability of the presence in palladium-based membrane alloys of two-dimensional lattice defects affecting the structure-sensitive properties of materials - packing defects (PD) - are assessed. The analysis of lattice imperfections of Pd93.5In6.0Ru0.5 (numerical indices-mass.%), Pd100-xPbx (x=5, 8, 12, 16, 20 mass.%) alloys was performed according to the results of X-ray diffraction using synchrotron radiation (SR) of the Kurchatov Research Center. The dependence of probability of PD formation on the concentration and grade of the palladium doping element has been established.
Show AbstractFilms of hafnium oxide HfOx with a thickness of about 40 nm were obtained by electron beam sputtering at different oxygen flow rates in the chamber. The electrophysical properties of films in air and vacuum were studied. It is shown that the temperature dependences of film conductivity, measured in vacuum in the temperature range from 20 to 180 °C, have an activation character with an activation energy of 0.82 ± 0.02 eV. It has been suggested that charge transfer in the resulting films is determined by the activation of electrons into the conduction band from the donor level associated with oxygen vacancies. It was found that the conductivity of films in air changes greatly with varying oxygen flow, while in vacuum the conductivity is practically independent of the oxygen flow. This indicates significant differences in the surface properties of films obtained at different oxygen flows in the chamber during the deposition process.
Show AbstractComposite Films (Сd$_3$As$_2$)$_{100-Х}$(MnAs)$_Х$ on silicon and sitall substrates with a concentration of Mn 5.8-16.4 at.% were obtained by vacuum-thermal evaporation. The structural properties of the films were investigated by X-ray phase analysis and scanning electron microscopy. Magneto-optical properties were studied by the transverse Kerr effect (TKE) in the energy range of 0.5-4.0 eV in magnetic fields with a strength of up to 3 kOe at a temperature of 20-300 K. In the geometry of the transverse Kerr effect, spectral, field and temperature dependences of the TKE are obtained. The analysis of experimental data showed that with a Mn content of more than 12.9 at.% of the films contain the α”-phase of the topological Dirac semimetal Cd3As2 in the form of large granules, as well as ferromagnetic MnAs granules. The Curie temperature of films depends on the Mn content in them and is less than the temperature of bulk samples of MPas. When the Mn content in the film is 5.8 at.% and 6.4 at.%, the magneto-optical response is not detected, which indicates the formation of a superparamagnetic state or a spin glass state at low concentrations of Mn. With a film content of Mn 9.9 at.% a significant change in magneto-optical spectra was detected, which indicates the formation of MnAs nanoclusters and partial dissolution of Mn in the Cd3As2 matrix.
Show AbstractThe spatiotemporal dynamics of the plasma of a symmetrical dual-frequency 81 MHz/1.76 MHz capacitive discharge under the influence of a low-frequency field of 1.76 MHz has been studied. Using the method of phase-resolved optical emission spectroscopy, the dynamics of the radiation intensity of argon and xenon in plasma was obtained. The electron energy distribution function at the center of the discharge was measured using a Langmuir probe and the electron density was measured using a microwave probe. The main result is the dynamics of the intensity ratios of the selected argon and xenon lines depending on different conditions: at pressures of 40, 200 and 400 mTorr, LF voltage amplitude of 100, 200 and 400 V, input power at 81 MHz of 3 W and 15 W. The dynamics of high-energy electrons is studied based on a two-temperature approximation of the electron energy distribution function.
Show AbstractIn this work we present an automatic thermoregulation system for biosensors based on field-effect transistors with a nanowire channel, which provides full control on the required temperature regime in bioanalytical analises. The system elements, including field-effect transistors with a nanowire channel, temperature sensors and heaters, were fabricated on a single silicon cristal using electron beam lithography, reactive ion etching and high-vacuum deposition techniques. Unicue electronics have been developed to control and maintain temperature. The dependence of thermometer readout on heating power was measured, which is in good agreement with the results of numerical simulation. A demonstration of a thermoregulation system with PID-feedback was carried out, ensuring the establishment of a desiered temperature in the range of 30-70 degrees in 18 seconds in liquid. A demonstration of a thermoregulation system for detecting nucleic acids was carried out using synthetic single-stranded DNA, which is a gene fragment from the bacterium Escherichia coli. The minimal detectable response was observed for a sample with a concentration of 3 fM.
Show AbstractThe unique Dsup protein of the tardigrade Ramazzottius varieornatus increases resistance to radiation and oxidative stress in various species of organisms and in human cell culture. According to modeling data, Dsup forms a complex with DNA with an intermolecular distance of ~4 Å, as a result of which DNA is less damaged by reactive oxygen species formed during exposure to radiation. However, the stability of the Dsup protein itself under the influence of ionizing radiation remains unclear, which is important for assessing its radioprotective potential and understanding the molecular mechanisms of the action of this protein under conditions of high doses of radiation. In this work, the radiation degradation of the Dsup protein after γ-ray irradiation by small-angle X-ray scattering (SAXS) and protein electrophoresis in polyacrylamide gel under denaturing conditions (SDS-PAGE) was studied for the first time. It has been shown that, in contrast to the control bovine serum albumin, the spatial and structural characteristics of the Dsup protein remain almost unchanged even when exposed to high doses of radiation (5 and 10 kGy), which suggests its high radiation stability.
Show AbstractA prototype of an infrared photometer created at the State Aviation Institute of Moscow State University on the basis of a commercial photosensitive module Gavin-615A is presented. The main spectral operating range of the photometer is 3-5~$\mu m$. Studies of the photometer detector have shown that its parameters correspond to those declared by the manufacturer. The nonlinearity of the detector does not exceed $\sim5\%$ over the entire range of signals; to correct it, the coefficients of the correction functions are determined. The readout noise $RN=1200\pm210$~e$^-$, the conversion factor GAIN~$= 520 \pm 9~e^{-}/$~ADU, the magnitude of the substrate frame signal BIAS~$= 960.5 \pm 2.2~ADU$ and dark current $\approx(9.3\pm1.1)\cdot10^6$~e$^-$/s, consisting of the sum of the dark current of the detector and the radiation of the input window of the sensitive module and measured by us at the temperature of the input windows $6^\circ$C are determined. Observations with the photometer began at the 2.5-m telescope of the Caucasus Mountain Observatory of MSU, the first results of which are presented in the work. The non-vignetted field of view was $30''$. In the $M$ band, under good atmospheric conditions, a diffraction image quality of $0.5''$ was achieved. During an accumulation time of 20~s with an SNR$\sim10$ ratio, images of a star with magnitudes $L=7.96$ and $M=6.78$ were obtained. It is shown that with high image quality, during an accumulation time of 20 seconds in the $L$ and $M$ bands with SNR=3, stars up to $\sim$9$^m$ and $\sim$8$^m$ can be observed, respectively. The main module of the photometer was also used to measure the brightness of the sky background.
Show AbstractOn the basis of the three-dimensional geodynamo model, it is shown that at small amplitudes of heat sources during reversals and excursions of the geomagnetic field, attenuation of not only the dipole magnetic field, but also the field of high harmonics is observed. In this scenario, the Earth's magnetosphere may be significantly smaller than previously expected, and the amount of radiation penetrating the Earth may be correspondingly greater.
Show AbstractThe analysis of the effect of high-energy protons of space radiation on the onboard electronics of the spacecraft is carried out. It is shown that protons can cause nuclear reactions with atomic nuclei of electronics material. The residual nuclei formed as a result of a nuclear reaction have sufficiently high energy to cross the sensitive areas of several bits of electronics, and the high ionizing ability of nuclear fragments allows generating an excess charge of carriers exceeding the critical charge for the failure to occur simultaneously in several bits of the electronic device
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