Том 42, № 8 (2016)

The operation of a membrane capacitive pressure transducer with electrostatic compensation of the membrane deformation has been mathematically simulated. It is shown that the theory describing these instruments is incorrect and the error in measuring pressure by them may be as high as 25–29% of the measured value, which makes them inappropriate for use in pressure metrology.

A diagnostic technique that is based on measuring the ratios of neutral-helium line strengths has been developed for peripheral distributions of electron temperature and density of tokamak plasma. The main components of the technique are a four-channel filter-lens imaging polychromator (FLIP-4) and a Phantom Miro M110 high-speed camera for recording the images. The polychromator has been assembled, adjusted, and tested on an optical test bench. The optical system was installed on the spherical Globus-M tokamak. Some preliminary experiments were carried out. Images of the plasma-gun jet were obtained at neutralhelium lines.

A new opportunity to analyze the atomic composition of thick (>100 μm) epitaxial GaAs layers by SIMS with lateral imaging of the cross section of a structure is demonstrated. The standard geometry of ldepth analysis turns out to be less informative owing to material redeposition from the walls of a crater to its floor occurring when the crater depth reaches several micrometers. The profiles of concentration of doping impurities Te and Zn and concentrations of Al and major impurities in PIN diode layers are determined down to a depth of 130 μm. The element sensitivity is at the level of 10¹⁶ at/cm³ (typical for depth analysis at a TOF.SIMS-5 setup), and the resolution is twice the diameter of the probing beam of Bi ions. The possibility of enhancing the depth resolution and the element sensitivity of the proposed analysis method is discussed.

A 3D numerical electromagnetic simulation of a vircator in the mode of electron-beam squeezedstate generation is performed. Detailed numerical investigations are carried out, and the dynamics of charged particles in the squeezed state is analyzed. It is shown that the electron beam density (and, as a consequence, effective beam plasma frequency) can be significantly increased in the squeezed state. Hence, the vircator generation frequency and power can also be increased.

The effect of physical and chemical properties of the gaseous medium on the formation of triple Mach configurations and vortex contact structures and on the stagnation pressure and drag force dynamics has been studied for supersonic flows with external energy sources. For the ratio of specific heats that varies in a range of 1.1–1.4, a significant (up to 51.8%) difference has been obtained for the angles of triple-shock configurations in flows at Mach 4 past a cylindrically blunted plate. When studying the dynamics of the decreases in the stagnation pressure and drag force, it has been revealed that these effects are amplified and the vortex mechanism of drag reduction starts to prevail as the adiabatic index decreases.

An immersion mass spectrometer with a membrane interface was used for oil detection and oil concentration measurements in seawater by measuring in situ the concentrations of three hydrocarbons: benzene, toluene, and xylene in the region of the specialized Primorsk oil loading seaport in the Gulf of Finland. The recorded mass spectra demonstrated the possibility of measuring the oil concentration in seawater and determining the grade of oil products. The use of a mass spectrometer with a membrane separator interface allows measurements of hydrocarbon concentration with high accuracy, which is currently not provided in commercially available monitors.

The magnetoimpedance of a film trilayer consisting of magnetically soft and magnetically hard films separated by a high-conductivity nonmagnetic spacer is theoretically investigated. A model for describing the dependences of the sample impedance on the external magnetic field and frequency is proposed, which is based on simultaneous solution of the linearized Maxwell and Landau–Lifshitz equations and takes into account the magnetostatic interaction between the magnetic layers. It is demonstrated that the magnetostatic interaction changes the distribution of magnetization of the magnetically soft film and leads to the occurrence of asymmetry in the field dependence of the impedance. The results obtained can be used in the development of weak magnetic field sensors.

Experiments on decomposition of carbon disulfide CS₂ in air under the action of a pulsed nanosecond corona discharge have been carried out. The energetic efficiency of the degradation amounted to 290–340 g (kW h)^–1, which is significantly higher than with the use of a corona discharge at a constant voltage. The main degradation products are sulfur dioxide SO₂, carbonyl sulfide COS, sulfuric acid, and carbon dioxide. Processes occurring in pulsed corona discharge plasma and leading to carbon disulfide degradation are considered. Different methods of air purification from carbon disulfide are compared.

It is established that the spectrum of spin wave (SW) resonance in garnet ferrite films with linear depth profile of the effective anisotropy consists (unlike the spectrum of homogeneous films) of a series of high-intensity SW modes and modes of very low intensity. The distribution of resonance fields of high-intensity SW modes depends on the gradient of the effective anisotropy field. For the same film thickness, the number of these modes increases with the value of gradient.

A new variant of the method of probability density distribution recovery for solving topical modeling problems is described. Disadvantages of the Gibbs sampling algorithm are considered, and a modified variant, called the “granulated sampling method,” is proposed. Based on the results of statistical modeling, it is shown that the proposed algorithm is characterized by higher stability as compared to other variants of Gibbs sampling.

The efficiency of first-order diffraction on F1 glass echelle gratings for soft X-ray and extreme UV radiation can be significantly increased (by up to ten times) by etching the groove surface with a beam of neutralized Ar ions at 1250-eV energy. The processing was performed at normal incidence of ion beam on the surface of gratings, and the material thickness removed was on a level of 80–300 nm. A principle of optimization of the ion-beam etching process is proposed for solving particular tasks related to the planarization of microstructures with various lateral dimensions.

We have theoretically studied the dynamics of molten metal during crater formation in the cathode spot of vacuum arc discharge. At the initial stage, a liquid-metal ridge is formed around the crater. This process has been numerically simulated in the framework of the two-dimensional axisymmetric heat and mass transfer problem in the approximation of viscous incompressible liquid. At a more developed stage, the motion of liquid metal loses axial symmetry, which corresponds to a tendency toward jet formation. The development of azimuthal instabilities of the ridge is analyzed in terms of dispersion relations for surface waves. It is shown that maximum increments correspond to instability of the Rayleigh–Plateau type. Estimations of the time of formation of liquid metal jets and their probable number are obtained.

A new type of f lux-gate vector magnetometer based on epitaxial yttrium iron garnet films has been developed and constructed for magnetocardiography (MCG) investigations. The magnetic field sensor can operate at room temperature and measure MCG signals at a distance of about 1 mm from the thoracic cage. The high sensitivity of the sensor, better than 100 fT/Hz^1/2, is demonstrated by the results of MCG measurements on rats. The main MCG pattern details and R-peak on a level of 10 pT are observed without temporal averaging, which allows heart rate anomalies to be studied. The proposed magnetic sensors can be effectively used in MCG investigations.

Application of nanostructured composite coatings with a quasi-zero refractive index synthesized using the proposed patented technology provides a 25–30% increase in the efficiency of solar cells as compared to that of analogous solar cells with traditional (e.g., silicon nitride) single-layer interference antireflection coating.

We describe a method of obtaining aerosol nanoparticles in a repetitive spark discharge generator with 12 interelectrode gaps between tin electrodes, which operates at a pulse repetition frequency of 2.5 kHz. During synthesis of tin oxide nanoparticles in air, the mass productivity of the gas discharge generator reaches up to 9 g/h for primary particles with characteristic sizes within 5–10 nm and agglomerate size on the order of 50 nm.