Instruments and Experimental Techniques最新文献

The main patterns of formation of focal spots of bremsstrahlung radiation during interaction of a betatron electron beam with various small-sized targets are investigated on the basis of a model previously determined in experimental and model studies of the method of measuring focal spots of bremsstrahlung radiation of betatrons with flat targets. The sizes of the focal spots depend on the ratio between the size of the target along the axis of the electron beam and the size of the target normal to the beam axis. Parallelepiped-shaped targets with appropriate size ratios form circular focal spots. The latest version of the method using a slit collimator determines the size of focal spots of small targets as the width of the distributions at half the height of normal approximations of the real distributions of quanta in the focal spots. The output of bremsstrahlung from a focal spot of a small target is much greater than the output from a secondary focal spot component of the same size when collimating bremsstrahlung emerging from a flat target.

The structure, composition, and algorithm of operation of the measuring and computing system for measuring the energy parameters of insolation (solar radiation) under terrestrial conditions are presented. The system is capable of making continuous measurements and recording of the energy parameters of insolation and solar activity using commercial silicon photovoltaic modules of monocrystalline and polycrystalline types as the sensing devices. Real-time measurements of open-circuit voltages, short-circuit currents, currents and voltages at operating points of modules, and temperatures of modules and the environment are performed. The recorded parameters are processed, the current−voltage characteristics of the modules are determined based on the analytical model of solar panels, and the generated power and energy are calculated for the required time interval. All necessary measured and calculated values are graphically displayed.

A prototype of a two-coordinate position-sensitive detector based on a RPC with a thin film converter (2 µm) made of boron carbide enriched in isotope ¹⁰B > 95% is presented. The active area size is 75 × 150 mm², which corresponds to 64 registration channels along the x axis and 128 channels along the y axis. The design of the detector, the results of diagnostics of converter films by the X-ray reflectometry method, the spectrum of conversion gamma radiation, and the results of measurements with a laboratory source ²⁵²Cf are presented.

The newly developed multi-pixel photon counter (MPPC), which is essentially single-photon avalanche photodiodes (SPAD) array, has a significant application prospect in the field of laser detection because of its unique room-temperature photon number resolution capability. The working modes of SPAD are usually divided into active quenching (AQ) mode and passive quenching (PQ) mode. It is generally believed that the PQ mode has a long recovery time and a low photon counting rate (PCR), making it unsuitable for high-speed photon counting situations. This paper demonstrated a photon counting module based on a specially designed passive quenching MPPC. The small-area SPAD cells and the bulk resistance quenching mode greatly reduce the recovery time of the SPAD cells, enabling the PCR even surpassing that of the photon counting modules in AQ mode. The PCR of the developed MPPC module can reach more than 80 Mcps just in the PQ mode, which has obvious advantages in PCR and has a good application prospect especially in space target detection.

The peculiarities of preparation of single crystals of yttrium-aluminum garnet doped with cerium and terbium optimized for use as X-ray scintillators are described. Their X-ray luminescent properties are considered. The results of application of one of these scintillators in the design of a two-dimensional X-ray detector are presented.

A study of the effects of the main ten destabilizing factors on the parameters of the converter’s power elements has been conducted. Converters operating in the switching mode create voltage and current ripples in the supply network and at the input of connected consumers. To reduce the magnitude of ripples, it is proposed to use circuits with an incomplete range of output-voltage adjustment, which form a constant unadjusted and a pulsed adjusted component in the form of consumed current and voltage at the input of the output filter. In such circuits, the unadjusted component provides the transmission of electricity to consumers without adjusting and filtering its parameters, and reducing the amplitude of the adjusted pulse component makes it possible to reduce the inductance of the chokes and the capacitance of the capacitors of the input and output filters and, therefore, to improve their weight and size. The dependence of the ripple ranges of the current of the chokes and the voltage across the filter capacitors on the magnitude of the relative pulse-voltage component has been established. This study was performed on a converter model created using the MATLAB Simulink program. The research results were obtained for circuits with incomplete and full ranges of output-voltage adjustment, analysis of which proved the prospects of the proposed scheme.

A compact IR spectrograph based on a line array of pyroelectric sensors and operating in the vicinity of 10-μm-wavelength has been developed. The development was motivated by various tasks requiring prompt measurement of the spectral characteristics of multifrequency radiation in this spectral range. The spectrometer’s performance was tested using a wavelength-tunable CO₂-laser. With a fixed position of the diffraction grating, the spectrometer covers a wavelength range of approximately 0.6 µm (wavenumber range of approximately 50 cm^–1) with a spectral resolution of approximately 0.02 µm (which is approximately 0.2 cm^–1), which allows one to reliably separate two adjacent CO₂-laser lines.

The operation and test results of the operating prototype of a high-voltage power supply with active suppression of output–voltage ripples are described. The frequency of the source’s master generator is 90 kHz, and the capacitance value of the diode–capacitive multiplication circuit is 10 nF. The device was tested at an output voltage of 1 kV and a load current of 1 mA. The settings are indicated with which the achieved peak-to-peak ripple amplitude of the output voltage does not exceed 150 μV with a dc output resistance of no more than 20 kΩ.

NiO–In₂O₃ composites were synthesized by the impregnation of indium oxide nanoparticles with nickel nitrate salt. The phase composition and microstructure, as well as the conductivity of composites over a wide temperature range, have been studied. The introduction of nickel oxide into the In₂O₃ leads to an increase in its resistance. The time distributions of the annihilation radiation of positrons have been studied in the obtained composites. The results are consistent with the data of studies of free volume in samples by low-temperature nitrogen sorption. The possibility of observing point-charged defects or their clusters in metal oxide composites by the positron method is demonstrated. A correlation is observed between changes in the resistance of impregnated indium oxide samples and the intensity of the positron component associated with annihilation in point-charged defects.

When a two-phase mixture moves along a pipeline section, energy is consumed. The energy consumption during the flow transport is determined by the pressure drop and the volumetric flow rate of the mixture. The dependence of the pressure losses during transportation of a two-phase flow on the volume and mass gas content is shown. A method for determining the gas content in a two-phase flow depending on the pressure loss value due to friction is presented. The basic calculation data for estimating the gas content in a two-phase flow depending on the pressure loss value for transporting a two- and single-phase flow with a similar mass flow are presented. The presented model of an experimental setup in the form of a pipeline section with piezometers for determining the pressure losses due to friction is designed to determine the content of gas impurities in the flow. When determining the pressure loss, a homogeneous model of a two-phase mixture was used as the most suitable with a low gas (vapor) content in the liquid flow. A schematic diagram of the setup that is used to study two-phase flows under laboratory conditions is presented as well.