No. 12

Cavity ring-down technique for high-reflectance measurement

The article describes a stand for measuring the specular reflection coefficient of more than 99,9 % by the method of intracavity attenuation using continuous-wave laser. The measurement method is based on the dependence of the rate of attenuation of laser radiation in an laser cavity after the continuous-wave laser is turned off on the reflection coefficient of the mirrors that make up this laser cavity. This method is completely immune to fluctuations in the power of radiation sources and provides high measurement accuracy. The results of measurements of the specular reflection coefficient are presented.

Keywords: reflection coefficient, optical coatings, thin films, laser cavity, laser, measuring stand, ion beam sputtering, cavity ring-down technique.

The effect of the heat treatment and radiation ray on the parameters of photocells based on silicon doped with impurity nickel atoms

The effect of high-temperature processing and the effect of ?-radiation on the parameters of obtained photocells based on silicon doped with impurity nickel atoms has been studied. It is shown that impurity nickel atoms increase the stability of the electrophysical parameters of photocells under the influence of both high temperatures and ray of ?-radiation. The results of the study found that addition of nickel impurity atoms to the volume of a silicon-based photocell forms clusters, which lead to temperature stability and radiation resistance of the short-circuit current, and open-circuit voltage parameters of photocells lead to an increase in efficiency.

Keywords: silicon, photocell, nickel, low-temperature annealing, cluster, gamma irradiation, degradation.

Repeater of the optical channel of speech information leakage

The paper considers a data transmission network based on visible light modulation as an integral part of the information leakage channel. The technical aspects of acoustic information transmission are reflected. The analysis of the possibility of relaying messages using visible light generated by LEDs by means of modulation is carried out.

Keywords: visible light modulation, LED, information leakage channel, acoustic information, information protection, repeater.

Determination of ionol degradation products in insulating petroleum oil by gas-liquid chromatography with a flame ionization detector

Transformer oil has been used for over 100 years as an insulating and heat dissipating medium in high voltage transformers. However, under the influence of various factors (high winding temperature, electric field, contact with air oxygen and metal parts of equipment), the oil undergoes oxidation, which leads to a deterioration in its dielectric properties. In order to slow down the process of oil oxidation and extend the life of liquid insulation, an antioxidant additive ionol (2,6-di-tert-butyl-4-methylphenol) is added to it. In the process of continuous operation, ionol is also subject to decomposition. In turn, the degradation products of the additive can serve as indicators of the state of the liquid insulation as a whole. Therefore, in this paper, we propose a method for determining the decomposition products of ionol in their joint presence in insulating mineral oil from operating high-voltage equipment. The analysis technique is based on the method of gas-liquid chromatography with a flame ionization detector and does not require significant investments when it is implemented in a power grid laboratory.

Keywords: mineral insulating oil, transformer oil, oxidation inhibitor, antioxidant additive, ionol (2,6-di-tert-butyl-4-methylphenol), gas-liquid chromatography with flame ionization detector.

Comparison of the results of experimental and theoretical studies of mechanical stresses during compression of an annular sample

This article presents the results of research on the use of acoustic methods for monitoring mechanical stresses (MN) in a triaxial stress state. For the purpose of scientific substantiation of experimental methods of ultrasonic control of MN, studies were carried out to measure the MN acting in the material of an annular sample during compression, and corresponding calculations for the evaluation of MN. Two sets of MN controls were used to measure MN when loading an annular sample. To calculate the MN acting in the sample material, computer modeling was used in the engineering analysis system COMSOL Multiphysics. The results of MN measurements using ultrasonic control methods and simulation results showed qualitative convergence, which confirms the possibility of using the selected methods for monitoring the triaxial stress state.

Keywords: mechanical stresses, ultrasound, acoustoelasticity, ring, compression.

Development of the Design of the Sensor and the Elements of Software Data Processing of the Dynamic Indentation Device

In this paper, the question of the possibility of using the magnetic induction method with differential inclusion of inductors for recording the motion parameters of a striker during dynamic indentation is considered. A prototype of the primary transducer is presented. A computer model has been developed for recording the movement of the striker during the flight and the sinusoidal movement of the magnet inside the coil. Experimental testing and comparative analysis of the results of computer simulation and experimental testing have been carried out.

Keywords: dynamic indentation, contact-impact interaction, registration system, motion parameters, magnetic induction method, coil, magnet.

Investigation of the application and calibration of DI-24 and DI-24-10 sensors in industrial water disinfection plants using UV radiation

Description of the principle and procedure for calibrating sensors DI-24 and DI-24-10. The use of sensors to control the level of ultraviolet radiation in hull units of the 5th series and in vertical tray modules of the Scientific and Production Association «Laboratory of Pulse Technology», Moscow. Sensors are calibrated during their manufacture, repair, recalibration, etc. The sensors are able to monitor the amount of UV radiation passing through the layer of running water from a low pressure UV lamp. Low pressure UV lamps emit 254 nm UV spectrum, which is the bactericidal range of the UV-C spectrum and is suitable for the disinfection of various environments and surfaces. Proper calibration of sensors DI-24 and DI-24-10 allows you to accurately determine the amount of harmful microorganisms in water by means of determining changes in the UV transmission of water.

Keywords: sensors, UV radiation, disinfection technology.

Adaptive choice of measurement data word length in data compression problems

The article discusses the possibility of using the method proposed by the authors for preprocessing data before compressing them based on changing the bit depth of the source data to build an adaptive compression subsystem. As an estimate of the effectiveness of the proposed processing, it is proposed to take the value of the second maximum of the normalized autocorrelation function. The presented results of the study show the fundamental possibility of using the considered preprocessing in compression subsystems. At the structural level, a variant of building an adaptive preprocessing subsystem is considered.

Keywords: data preprocessing, data compressing, word length, autocorrelation function, information and measuring system.

Manufacturing and testing of a dual-axis scanning head

The article discusses the results of the development of a previously designed two-axis scanning head for the implementation of an additive process of selective laser melting of metal powders. The head is designed to work with a ytterbium continuous laser with a wavelength of 1.08 ?m in a working field of 300 х 300 mm. The head includes a collimator, two galvo motors with scanning mirrors and rotation angle sensors, and an F-theta lens. The three-lens collimator expands the beam to a size of 15 mm, has a lens diameter of 25.4 mm and an additional option of water cooling. Scanning mirrors are made of single-crystal silicon and have a mirror coating with a specular reflection coefficient exceeding 99.6 %. The design uses an absolute optical sensor of the angle of rotation of the motor rotor shaft. The mirror and sensor are driven by a brushless DC torque motor with a moving magnet rotor. The four lenses of the F-theta lens are made of optical quartz and have an anti-reflective coating that ensures that over 99.7 % of the working radiation passes through each optical surface. The developed electronic control board controls the galvo motors and the laser radiation source, ensuring the positioning of the laser beam with a given accuracy in the product construction zone.

The manufactured scanning head was tested for performance according to the developed program and methodology on a special stand and equipment specially made for testing. As a result of testing, the main design characteristics (sizes of the working field and scanning angles, scanning step, scanning speed and positional repeatability, temperature zero shift and long-term drift) were exceeded in relation to the requirements of the specification. Further research will be aimed at reducing the size of the focal spot over the entire working field.

Keywords: scanning head, scanator, scanning mirror, galvo motor (galvo), rotation angle sensor, functional testing, positional repeatability, scanning/positioning speed, focal spot size.