Technical Physics Letters最新文献

The TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) is a 4 m imaging atmospheric Cherenkov telescope designed for very high-energy (VHE) gamma-ray observations and has been operational at Mount Abu, India, for over two decades. The telescope’s light collector has recently been upgraded to a tessellated structure comprising 34 spherical mirrors fabricated from single-point diamond-turned aluminum alloy (Al 6061-T6). Each mirror has a diameter of 600 mm and a focal length of ~4000 mm. Previously, the telescope employed glass mirrors of the same diameter, which required frequent aluminization due to degradation of reflectivity under prolonged atmospheric exposure. In this work, we present qualification studies of the diamond-turned metallic mirrors to evaluate their optical performance and environmental durability for Cherenkov light collection in the 300–700 nm wavelength range. The characterization includes spot size measurements using the 2f method, surface roughness evaluation, reflectivity assessment, and water ingress testing. Additionally, ray-tracing simulations were performed using ROBAST to estimate the point-spread function (PSF) for all 34 mirrors of the TACTIC telescope. The results demonstrate that the developed mirrors satisfy the required specifications and are suitable for long-term operation under site-specific environmental conditions.

The energy parameters of plasma-electrolyte spraying leading to the formation of hollow SiO₂ particles from an aqueous solution of Na₂SiO₃ (5 wt % by SiO₂) in a 300-mL reactor were studied. The discharge was excited at the end of a hollow steel cathode tube by rectangular pulses with a duration of 50 μs and an amplitude of up to 300 V. Modes with a frequency of 5 and 20 kHz were compared. Oscillograms U(t) and I(t), the change in the mass of the solution, and the heating and thermal field of the wall, as well as the yield and morphology of the solid product, were recorded. At 5 kHz, the average power obtained was 75 ± 5 W and the yield was 5.5 ± 0.2 g SiO₂ in 10 min; at 20 kHz, 270 ± 10 W and 11.4 ± 0.3 g in 10 min. The specific energy of synthesis was 8.1 ± 0.6 and 14.2 ± 1.2 kJ/g, respectively. The energy balance showed that, at 5 kHz, the main expenses are due to heating the solution and evaporation of water (a total of ~95%), while at 20 kHz a significant share is taken up by heat removal through the wall and electrode. According to morphological analysis, hollow spherical particles with a diameter of 3–15 µm predominate; an increase in frequency decreases the median diameter and increases the proportion of hollow particles. The obtained relationships between the supplied energy, phase transitions, and product yield were used to formulate ways for optimizing the pulse mode.

A single-stage plasma-electrolyte method for the synthesis of hollow particles of silicon dioxide (SiO₂) from an aqueous solution of liquid glass without the use of solid templates. A contact glow discharge in the electrolyte was maintained by a dc source with smooth regulation of the output voltage in the range of 0–400 V and a current of 0–10 A in an alkaline solution of Na₂SiO₃ (≈5 g/L SiO₂, pH ≈ 12). The morphology of the obtained particles was studied using scanning electron microscopy (SEM). It was found that the main product is hollow spherical particles with a diameter of 0.5–2 µm (D₅₀ ≈ 1.1 µm). Based on SEM images of the destroyed spheres, the shell thickness was estimated to be about 50–120 nm, which corresponds to a relative thickness of t/D ≈ 0.05–0.10. The mechanism of formation of hollow spheres and possible areas of application of the obtained microspheres as lightweight fillers and platforms for subsequent functionalization are discussed.

The study examined the influence of bore gauge measurement errors on the formation of the number of incorrectly accepted and incorrectly rejected bushing holes under the camshaft journals cylinder blocks of YaMZ engines. The rationality of using the most accurate bore gauge from a range of universal instruments that satisfy the basic conditions for selecting measuring instruments has been scientifically substantiated and practically proven; otherwise, even if the selection condition is met, the percentage of losses increases in the form of sending such expensive parts as cylinder blocks to scrap.

Results of research in the field of improving diagnostic methods for the technical condition of the component base of technological machines, in particular, hydraulic drives, are presented. It is proposed to assess the condition of the elements of hydraulic systems of technological machines on the basis of vibroacoustic analysis. Using the example of a gear pump, informative signs in the vibration signal for various types of malfunctions, including wear of bearings and gears, are highlighted. The effectiveness of spectral analysis in terms of power spectral density for defect identification has been proven, which has shown consistent patterns under various operating modes. The method includes a modification with the inclusion of a developed software package for automated signal processing and control decision-making in the diagnostic apparatus. The technique allows a transition to be made from a traditional scheduled maintenance system to maintenance based on condition, adjusting the resource of the hydraulic drive of technological machines for various purposes in real time.

A comprehensive study of the radial inhomogeneity of the plasma of a mixture of 75% HBr + 25% Cl₂ under conditions of induction RF (13.56 MHz) discharge in the pressure range of 0.8–2.8 Pa and power of 800–1600 W has been carried out. The profiles of radial distribution of concentrations of charged and neutral active particles have been established by methods of probe diagnostics and modeling. It is shown that (a) the best isotropy of the plasma in terms of electron concentration and ion flux is achieved at the upper boundary of the pressure range studied; and (b) the unequal concentration profiles of chlorine and bromine atoms cause a significant (especially at low pressures) change in the [Cl]/[Br] ratio from the center to the periphery.

The article presents the results of studies of plasma–liquid welding of copper plates. Copper plate products were welded in an electrolytic solution using plasma–liquid systems. A technological installation was used for welding, which produced a constant voltage of the required values. A liquid electrolyte was used as the positive electrode, and welded parts were used as the negative electrode. The resulting weld was checked for unwanted inclusions and pores, and the chemical composition of the weld and the Vickers hardness were determined. During the plasma–liquid welding process, the values of current and voltage were measured, according to which the characteristics of current and voltage from time were compiled.

This work presents the mechanism of formation of columnar hafnium nitride-titanium nitride (HfTiN₂) coating crystals by cathodic arc deposition, followed by treatment with a flux of low-energy argon ions generated in a low-pressure radio-frequency capacitive discharge. A model of low-energy ion bombardment of the coating was developed using the molecular dynamics method.

The photocatalytic activity of titanium oxide films deposited by reactive magnetron sputtering on carbon and glass fabric was studied. It has been shown that the efficiency of decomposition of methylene blue dye under the influence of UV radiation depends to a large extent on the structure of the catalyst film and the type of substrate on which it is applied.