Showing papers in "Instruments and Experimental Techniques in 2019"
TL;DR: In this article, the characteristics of the quasi-monochromatic calibration beam of secondary electrons at the Pakhra accelerator (Lebedev Physical Institute) on the basis of the SP-57 magnet are presented.
Abstract: The characteristics of the quasi-monochromatic calibration beam of secondary electrons at the Pakhra accelerator (Lebedev Physical Institute) on the basis of the SP-57 magnet are presented. The energy resolution of the beam with a copper converter 0.1–5.0 mm thick and an interpolar magnet gap of 6 cm is δ = 10.0–4.5% in accordance with the energy in the electron-beam energy range E = 98–294 MeV.
13 citations
TL;DR: A method for multiple mutual synchronization of parallel computational threads, which is used in spectral-domain optical coherence tomography systems, is described and made it possible to perform procedures for calculating tomographic slices of the subsurface tissues of a living organism in real time.
Abstract: —A method for multiple mutual synchronization of parallel computational threads, which is used in spectral-domain optical coherence tomography systems, is described. Due to the effective distribution of the computational load in the central processor of the control computer, the method made it possible to perform procedures for calculating tomographic slices of the subsurface tissues of a living organism in real time. The application of this method made it possible to realize the principle of multimodal optical coherence tomography and achieve significant results in a number of medical and biological studies.
10 citations
TL;DR: In this paper, a review of several new methods for increasing the main functional parameters of deflectors, which were realized in devices, is presented, which makes it possible to significantly increase the diffraction efficiency, extend the scanning range, and create a polarization-insensitive deflector.
Abstract: Deflectors that are based on the Bragg nonaxial anisotropic diffraction in a paratellurite crystal are considered. Practically significant relationships were obtained and factors that limit the diffraction efficiency and the angular scanning range were determined. A review of several new methods for increasing the main functional parameters of deflectors, which were realized in devices, is presented. In particular, a double-crystal deflector scheme is considered, which makes it possible to significantly increase the diffraction efficiency, extend the scanning range, and create a polarization-insensitive deflector. It is shown that the diffraction mode in the second Bragg maximum (with respect of the acoustic amplitude) can be used for bandwidth broadening. It is proposed to use a two-element optimally phased piezoelectric transducer for extending the frequency scanning range.
10 citations
TL;DR: In this paper, the main active factors of the spark plasma sintering process, the nature and degree of their influence on the mechanism of consolidation of particles of powder mixtures, as well as the structure and properties of synthesized ceramics are determined.
Abstract: The design of a laboratory apparatus for spark plasma sintering of powder compositions of different compositions and purposes is described. The main active factors of the spark plasma sintering process, the nature and degree of their influence on the mechanism of consolidation of particles of powder mixtures, as well as the structure and properties of the synthesized ceramics are determined. The data on the synthesis of 25.4 mm ceramic disks of samarium monosulfide powder are given. It is shown that the optimization of the synthesis regimes allows one to obtain a compacted material with a density close to the theoretical one and a phase composition identical to the composition of the initial powder mixture.
10 citations
TL;DR: In this article, the results of the development of a synchronization system (modulator) of two active elements based on copper bromide vapors are presented, and the main features of its design and operation are described.
Abstract: —The results of the development of a synchronization system (modulator) of two active elements based on copper bromide vapors are presented. The main features of its design and operation are described. The working capacity of the device was investigated in a master oscillator–power amplifier system (MOPA system), for which the amplification characteristic was obtained. The modulator formed trigger pulses with rise times of at most 100 ns that were fed to the grids of TGI1-1000-25 thyratrons. The time shift between the triggering of the thyratrons is adjusted using a variometer with a positioning accuracy of no worse than 1 ns. The maximum time shift between pulses is 55 ns and it can be increased via the use of additional cable delay lines.
9 citations
TL;DR: In this article, a high-power source of ultrawideband radiation based on the synthesis of electromagnetic pulses with different frequency bands has been created, and a four-channel former of highly stable bipolar pulses with durations of 0.5 and 1 ns was developed.
Abstract: —A high-power source of ultrawideband radiation based on the synthesis of electromagnetic pulses with different frequency bands has been created. A four-channel former of highly stable bipolar pulses with durations of 0.5 and 1 ns was developed. Each element of a 2 × 2 array of combined antennas was excited from its former channel. Two modes of radiation synthesis were studied: according to the maximum field strength and the maximum spectrum width. For the first mode, radiation pulses with a frequency band of 0.39–2.13 GHz and an effective potential of 600 kV were obtained. Synthesized radiation pulses with an extended frequency band of 0.15–2.7 GHz and an effective potential of 200 kV were obtained in the second mode. The pulse repetition frequency was 100 Hz.
8 citations
TL;DR: In this paper, the results of pilot studies of silicon shock-ionized dynistors (SIDs), which belong to the class of thyristor-type semiconductor devices that are able to be switched to a highly conducting state within a time shorter than 1 ns upon application of a short overvoltage pulse that initiates an impact-ionization process, are presented.
Abstract: The results of pilot studies of silicon shock-ionized dynistors (SIDs), which belong to the class of thyristor-type semiconductor devices that are able to be switched to a highly conducting state within a time shorter than 1 ns upon application of a short overvoltage pulse that initiates an impact-ionization process, are presented. The excellent characteristics of SIDs in the mode of switching high-power current pulses of nanosecond duration are demonstrated. Experiments are described that indirectly confirm the ability to initiate the process of subnanosecond switching of an SID by holes that are injected from a p+ emitter.
6 citations
TL;DR: In this article, the 109Cd γ-ray source was used to calibrate the energy scale of a two-phase argon detector for dark matter search and low-energy neutrino experiments.
Abstract: A two-phase argon detector is being developed in our laboratory for dark matter search and low-energy neutrino experiments. A 109Cd γ-ray source was used to calibrate the energy scale of the detector. In this paper, a detailed emission spectrum of the 109Cd source was measured using a YAP:Ce based scintillation detector and high-purity germanium detector. It was shown that the 109Cd source equipped with a tungsten substrate and a copper filter can provide a complete set of γ-ray lines in the range from 8 to 90 keV for energy calibration of two-phase detectors. These measurements allowed us to successfully quantify the shape of the amplitude spectrum observed when the two-phase detector was irradiated by the 109Cd source.
6 citations
TL;DR: In this article, a highvoltage device for generating low-temperature plasma in water that is saturated with air bubbles is considered, which contains a discharge chamber and a generator of voltage pulses with an amplitude of 30 kV and a rise time of 5 μs, which is able to form spark discharges with an energy of 1 J at a frequency of several hundred hertz.
Abstract: A high-voltage device for generating low-temperature plasma in water that is saturated with air bubbles is considered. It contains a discharge chamber and a generator of voltage pulses with an amplitude of ~30 kV and a rise time of ~5 μs, which is able to form spark discharges with an energy of ~1 J at a frequency of several hundred hertz. The electric circuit of the generator of discharges in water, which provides its high efficiency, and the design of the discharge chamber, which allows formation of parallel air flows through the water-filled interelectrode gap, are described. The results of studies of electric-discharge processes and the results of the chemical analysis of water samples that are enriched with products of plasmochemical reactions are presented. The possibility of the accelerated development of plants that are irrigated with plasma-treated water is shown.
5 citations
TL;DR: In this article, a technique for measuring the rate of change in the breakdown-channel resistance and estimating the true amplitude and duration of the breakdown current was developed, based on the dependence of the amplitude and frequency of oscillations of the measured current on the channel resistance.
Abstract: A technique for measuring the rate of change in the breakdown-channel resistance and estimating the true amplitude and duration of the breakdown current was developed. This technique is based on the dependence of the amplitude and frequency of oscillations of the measured current on the channel resistance. The resistance of the breakdown channel and the breakdown current in a polymer dielectric film were determined.
5 citations
TL;DR: In this article, a broadband highly efficient piezoelectric transducer (PET) for generating a slow acoustic mode in an acousto-optic paratellurite crystal is presented.
Abstract: The technology for creating a broadband highly efficient piezoelectric transducer (PET) for generating a slow acoustic mode in an acousto-optic paratellurite crystal is based on the acoustic matching of a lithium-niobate transducer to paratellurite using the method of galvanic deposition of an intermediate tin layer. A thin heat-conducting liquid layer between the heat sink and PET is used to remove heat from the PET without acoustic damping. A broadband highly efficient deflector with a center frequency of ultrasound of 37 MHz, a frequency band of more than 30 MHz, and a diffraction efficiency of more than 90% at a wavelength of 1.06 μm was created. A stable continuous operating mode of the deflector at acoustic-wave intensities of more than 20 W/cm2 has been achieved.
TL;DR: In this article, a system for detecting the clamping point of a manipulator tip based on the probe of an atomic-force microscope operating in the hybrid mode was proposed and implemented.
Abstract: A system for detecting the clamping point of a manipulator tip based on the probe of an atomic-force microscope operating in the hybrid mode was upgraded. The upgrading of the detection system made it possible not only to obtain topographic images of surfaces in this mode with vertical noises smaller than 10 nm, but also to use this manipulator to move microdroplets over the surface of a substrate. A method was proposed and implemented for moving nanowires using a fluid flow created by the tip of an atomic-force microscope.
TL;DR: In this paper, the process of searching for and determining subsurface delamination and inconsistency defects by a contactless optical method based on shearography is shown, which works on the principles of interferometry and holography.
Abstract: The results of measuring the deformation of products manufactured by methods of additive technologies are presented. The process of searching for and determining subsurface delamination and inconsistency defects by a contactless optical method based on shearography is shown. This method works on the principles of interferometry and holography. The slightest displacement of the surface can be measured with it with an accuracy on the order of the wavelength of light. A calibration device that reproduced the surface deformation was used to adjust the shearograph. The results of experimental studies show high sensitivity to small deformations of products, which is approximately 0.2 µm.
TL;DR: In this article, a series of articles is devoted to the study of high-power AC plasma torches with different designs, purposes, and characteristics that allow the operation of a certain type of plasma generator in wide power and pressure ranges.
Abstract: This series of articles is devoted to the study of high-power AC plasma torches with different designs, purposes, and characteristics that allow the operation of a certain type of plasma generator in wide power and pressure ranges. The first part is devoted to the investigation of AC plasma torches with a specific purpose, that is, the initiation of an arc of a powerful PT. This paper describes the design features of a PT in detail, its characteristics, the parameters of the plasma stream, such as temperature, and heat content. The features of operation and various options of auxiliary plasma torch injectors that provide ignition of the main arc in the electric-discharge chamber are considered as well.
TL;DR: In this article, the design of a laboratory hydraulic press with a force of 20 t was described, and a special feature of the press is the use of a spring for reversing the piston, which makes the hydraulic system particularly simple and simplifies the operating procedure.
Abstract: The design of a laboratory hydraulic press with a force of 20 t is described. A special feature of the press is the use of a spring for reversing the piston, which makes the press hydraulic system particularly simple and simplifies the operating procedure.
TL;DR: In this article, a detailed description of laboratory techniques and equipment used for measurements of a velocity field under regular standing surface waves in vicinity of a rigid vertical wall is presented, and the available data are used to calculate water particle trajectories of a standing wave system.
Abstract: The paper presents a detailed description of laboratory techniques and equipment used for measurements of a velocity field under regular standing surface waves in vicinity of a rigid vertical wall. The waves are generated in a closed flume by a monochromatic motion of a piston-type wavemaker and are reflected at a wall installed in a wave flume. A superposition of incident and reflected waves forms a standing wave. Particle image velocimetry technique is employed to measure evolution of a velocity field of wave-induced flow. The available data are used to calculate water particle trajectories of a standing wave system. Thus, a complete information on standing wave kinematics is obtained. The experimental results confirm that mass transport in Eulerian and Lagrangian sense cancels out in case of two progressive waves of lower steepness forming a standing wave. The experimental data may serve as a reference basis for theoretical models of waves interacting with vertical barriers. Moreover, important conclusions regarding the design of improved experimental setup leading to a better description of spatiotemporal velocity distribution under wavy surface are formulated.
TL;DR: An integral method for processing xenon used as a working medium in the RED-100 two-phase emission detector constructed in the NRNU MEPhI to study the process of elastic coherent neutrino scattering off atomic nuclei is described in this paper.
Abstract: An integral method is described for processing xenon used as a working medium in the RED-100 two-phase emission detector constructed in the NRNU MEPhI to study the process of elastic coherent neutrino scattering off atomic nuclei. The developed technology for purifying xenon and the detector has made it possible to increase the lifetime of quasi-free electrons in the 205-kg liquid xenon from ≤0.1 to ≥400 μs in fields of 50−500 V/cm. The entire procedure takes approximately 1000 h. The method can be used to process working media for new-generation two-phase emission detectors designed to conduct basic research, in particular, searching for dark matter in the form of weakly interacting massive particles, detecting boron solar neutrinos, and searching for neutrinoless double-beta decay.
TL;DR: In this article, a high-voltage power supply for a microfocus X-ray tube with the output voltage adjustment range of 30-80 kV at a power of 20-240 W was developed.
Abstract: A high-voltage power supply for a microfocus X-ray tube with the output-voltage adjustment range of 30–80 kV at a power of 20–240 W (the X-ray tube emission current is up to 3 mA) was developed. The source is based on a resonant voltage converter that provides switching of power switches at a zero voltage or a zero current. The source uses a method for controlling the output voltage by changing the supply voltage of the resonant-converter power stage. The use of the Silagerm-2106 modern organosilicon compound for high-voltage insulation of the circuit elements made it possible to additionally reduce the size of the circuit and place it together with the tube-cathode power supply and the module of communication with a PC in a standard 19-inch housing; the mass of the device is 21 kg.
TL;DR: In this article, the results of using a dynamic magnonic crystal, which is created by a surface acoustic wave (SAW) in the structure of a film of yttrium iron garnet on a gallium gadolinium garnet substrate, for the development of a tunable non-reciprocal microwave filter are presented.
Abstract: The results of using a dynamic magnonic crystal, which is created by a surface acoustic wave (SAW) in the structure of a film of yttrium iron garnet on a gallium gadolinium garnet substrate, for the development of a tunable nonreciprocal microwave filter are presented. A filter prototype that operates in the range of 3600–4200 MHz at a magnetic bias field of 640 Oe was developed and its main characteristics were measured. At a SAW frequency of 41 MHz and a power of 30 mW, the rejection depth was 23 dB. A SAW-frequency change by 1 MHz shifted the rejection frequency by ~7 MHz. The inversion of the signal-propagation direction in the device resulted in a shift of the rejection frequency by the value of the SAW frequency. The possibilities of the further improvement of the parameters of this device are discussed.
TL;DR: In this article, a photonic crystal fiber (PCF) was spliced to a well-cleaved singlemode fiber (SMF) and a multimode fiber (MMF), and the section of PCF was the cavity.
Abstract: The paper presents a FPI sensor by splicing a photonic crystal fiber (PCF) to a well-cleaved single-mode fiber (SMF) and a multimode fiber (MMF), preparing a SMF–PCF–MMF structure, and the section of PCF was the cavity. Temperature and NaCl solution concentration responses were investigated experimentally. The temperature sensitivity is ∼12.3 pm/°C and concentration sensitivity is ∼0.01 dB/%. The proposed sensor could offer such features as low cross-sensitivity, good temperature stability, temperature and concentration linearity are both over 0.996, making it attractive for liquid concentration and temperature measurement.
TL;DR: In this paper, an apparatus for conducting chemical reactions with microwave heating of reagents was developed, consisting of a microwave oscillator based on a domestic magnetron with deep regulation of the microwave power level and a device for microwave heating, which is a microwave reactor that contains a high-Q cavity resonator and a chemical reactor built into it.
Abstract: An apparatus for conducting chemical reactions with microwave heating of reagents was developed. It consists of a microwave oscillator based on a domestic magnetron with deep regulation of the microwave-power level and a device for microwave heating, which is a microwave reactor that contains a high-Q cavity resonator and a chemical reactor built into it.
TL;DR: In this paper, the design of a diamond neutral-particle spectrometer (DNPS) is presented, which is a part of the neutral particle analyzer (NPA) at the International Thermonuclear Experimental Reactor (ITER).
Abstract: The design of a diamond neutral-particle spectrometer (DNPS) is presented. The DNPS is a part of the neutral particle analyzer (NPA) at the International Thermonuclear Experimental Reactor (ITER). The operating modes of the DNPS in the NPA complex, the advantages of the DNPS, and its limitations are described. The DNPS system includes two diamond detectors that differ in sensitivity by a factor of 9. The energy losses in detector contacts are numerically estimated. The test results for the diamond detector are presented.
TL;DR: In this paper, a hybrid photo injector is presented for the Schlesinger center for compact accelerators in Ariel University, which is composed of a standing wave section (3.5 cells) and a traveling wave section(9 cells) in a single structure.
Abstract: A novel hybrid photo injector is being commissioned at the Schlesinger center for compact accelerators in Ariel University. The hybrid gun is composed of a standing wave section (3.5 cells) and a traveling wave section (9 cells) in a single structure, and therefore has a much larger inner surface than a typical 1.5 cell electron gun. This gun will be driving a THz Free Electron Laser (FEL), operating at the super-radiance regime, and therefore requires extraordinary beam properties. First operation of the RF gun was in January 2018. High-power RF field entering a metallic cavity can severely damage the RF structure or the RF window. For this reason, in order to achieve the desired high-field gradients in the RF gun, a careful and extensive conditioning work on the gun is required. This is done by applying slowly increasing power levels into the structure, while monitoring the response constantly. To increase the efficiency and safety aspects of the conditioning work, we developed in-house routines and interlocks, controlled by a dedicated software. Methods and information of diagnostics elements in the RF system are presented, and the necessary requirements to simplify the conditioning work are outlined.
TL;DR: In this paper, the electronics for functional units of the polarized-neutron reflectometer (PNR) were presented, and the electronic system connected the reflectometer units to the PNR control computer and provided control of step motors and absolute sensors for moving the experimental equipment.
Abstract: The electronics for functional units of the polarized-neutron reflectometer (PNR) is presented. The electronic system connects the reflectometer units to the PNR control computer and provides control of step motors and absolute sensors for moving the experimental equipment, specification and change of the parameters of devices during operation, and acquisition of experimental data in the graphic and digital forms. Devices developed by the Petersburg Nuclear Physics Institute are also included in the electronic system.
TL;DR: In this article, the possibility of using induction sensors for fixing hypersonic particles in time in the simulation of collisions of high-velocity metal particles with targets is considered, and a design of the induction sensor for starting the recording equipment in the air atmosphere is presented.
Abstract: The possibility of using induction sensors for fixing hypersonic particles in time in the simulation of collisions of high-velocity metal particles with targets is considered. A design of the induction sensor for starting the recording equipment in the air atmosphere is presented. Experimental results on the interaction of particles with air were obtained.
TL;DR: In this article, the results obtained in the study of the avalanche process of electron multiplication in a thick gas amplifier of a new design are presented, where the main feature of the device is the separation of the upper and lower parts of the amplifier by a gas gap with the preservation of the polyimide film as an insulator on the inner surface of the hole electrodes.
Abstract: The results obtained in the study of the avalanche process of electron multiplication in a thick gas amplifier of a new design are presented. The main feature of the device is the separation of the upper and lower parts of the amplifier by a gas gap with the preservation of the polyimide film as an insulator on the inner surface of the hole electrodes. The width of this gap can vary in the range of 0.1–1.0 mm, depending on the electrode size. With this separation, the surface leakage currents are absent between the electrodes and the charge is not induced on the inner surface of the gas-discharge gap. Due to this solution, it is possible to minimize the probability of both surface and volume streamer phenomena that turn into a Geiger or spark discharge. As a result, a pulse amplitude of a few volts was measured across a load of 50 Ω in a gas mixture of Ar + 20% CO2 when the detector was irradiated with a 90Sr β source.
TL;DR: The onboard data-acquisition system for the new-generation Yak-42D Roshydromet research aircraft, intended for investigating the atmosphere and the underlying surface, and the solution to the problem of synchronizing the data of high-frequency measurements are presented.
Abstract: The onboard data-acquisition system for the new-generation Yak-42D Roshydromet research aircraft is described. The research aircraft is intended for investigating the atmosphere and the underlying surface. The large quantity of scientific equipment installed onboard requires that the tasks of acquisition, synchronization, transmission, and storage of aircraft observation data be performed. The onboard measuring and computing system developed for the research aircraft and the local computer network are described. The solution to the problem of synchronizing the data of high-frequency measurements is presented. The possibilities of using the local network for integrating the measurement systems on board the research aircraft are shown. The principles of organization of a unified data-acquisition system can be used to build measuring systems for any class of mobile laboratory.
TL;DR: In this article, the design, principle of operation, and results of tests of a Fourier-transform spectrometer, which was designed for studying the composition of the Martian atmosphere by the transmission technique, are described.
Abstract: The design, principle of operation, and results of tests of a Fourier-transform spectrometer, which is designed for studying the composition of the Martian atmosphere by the transmission technique, are described. A standard specimen of the instrument must operate on the landing platform after its delivery to Mars. The spectral range of the manufactured specimen is 0.5–4 μm, the spectral resolution is 0.04 cm–1, the aperture is 25 mm, and the mass is 1.1 kg.
TL;DR: In this paper, an ellipsometer with switching of orthogonal polarization states is described, whose main feature is the use of a dual radiation source and Glan-Thompson polarization prisms from calcite with mixing and separation of Orthogonally polarized beams.
Abstract: An ellipsometer with switching of orthogonal polarization states is described, whose main feature is the use of a dual radiation source and Glan–Thompson polarization prisms from calcite with mixing and separation of orthogonally polarized beams. High reproducibility and stability of measurements of ellipsometric parameters Ψ and Δ in the spectral range of 400–2200 nm were achieved. With an integration time at each point of 2 s, the rms noise at a wavelength of 800 nm and a silicon oxide thickness of 450 nm for Ψ and Δ was 0.0025° and 0.016°, respectively. The RMS noise at a wavelength of 1800 nm and a silicon oxide thickness of 513 nm for Ψ and Δ was 0.005° and 0.03°, respectively.
TL;DR: In this paper, a laboratory technology for manufacturing iridium-yttrium cathodes, which are totally or locally coated with yttria, was developed, and a technique for determining the emissivity on the iridium surface was proposed and its value was determined.
Abstract: A laboratory technology for manufacturing iridium–yttrium cathodes, which are totally or locally coated with yttria, was developed. A technique for determining the emissivity on the iridium surface was proposed and its value was determined: 0.6 at a wavelength of 665 nm. The work function of such film cathodes was determined: eφ = 3.4 eV. The temperature range of the cathode operation under the conditions of a medium vacuum was established, and it was shown that this operation is efficient only for Т ≥ 1600 K. A physical model for describing this process is proposed. The high thermal stability of yttria-based cathodes, which can withstand heating at Т = 2500 K for hours without degradation, is shown.