Instruments and Experimental Techniques最新文献

A technique for preparing gaseous radioactive ³⁷Ar isotope under laboratory conditions by irradiating calcium metal with neutrons from a neutron generator is described. This isotope is used to calibrate the RED-100 two-phase emission detector designed to study coherent elastic neutrino−nucleus scattering.

This article discusses a difference method for measuring nonlinear signal distortions in digitizing devices. This method does not require the test signals to be strictly identical in shape. This allows for measuring nonlinear distortions in the picosecond range, where precise control of test signal shape is difficult. It is proposed to use test signals of different polarities for the simplicity of generating such pairs. Since the static nonlinearity of recording devices typically has a quadratic form, nonlinear distortions in the responses to such signals do not compensate each other. It is shown that, for given test signals in selected digitizing devices, nonlinear distortions of 0.1% or greater are observable, while nonlinear distortions introduced by digitizing devices are at least 0.4–0.5%. A technique for selecting dynamic nonlinear distortions is presented in which the static nonlinearity of the device is measured separately and then excluded from the measurement results. It has been shown that the polarity of dynamic nonlinear distortions can either coincide with the polarity of total nonlinear distortions or have the opposite polarity. It has been estimated that the maximum magnitude of dynamic nonlinear distortions is approximately comparable to the magnitude of static distortions.

This paper presents the design and preliminary validation of a non-contact microwave level measurement system tailored for corrosive and radioactive liquids in high-temperature environments, such as lead–bismuth eutectic at 800°C. The primary objective was to develop a safe, reliable, and long-life alternative to conventional contact-type sensors, which are prone to rapid degradation under such extreme conditions. A 24 GHz frequency-modulated continuous-wave (FMCW) radar configuration was selected due to its superior short-range accuracy. The system incorporates several novel design features: a conical horn antenna optimized for narrow beamwidth, a quartz-based microwave window, and a stainless-steel S-shaped circular waveguide that simultaneously enables efficient microwave propagation and effective gamma radiation shielding. Signal processing combines fast Fourier transform (FFT) and chirp Z-transform (CZT) algorithms to enhance intermediate frequency estimation, thereby improving range resolution. Experimental validation on a laboratory test bench demonstrated input matching of antenna better than 15 dB and confirmed the feasibility of centimeter-level resolution. FFT-based processing showed limited sensitivity to small distance variations, whereas the CZT approach successfully detected 1 cm positional changes, though with non-linear response linked to oscillator control voltage non-linearity. Future work will focus on correcting non-linearities and deploying the system in harsh environments.

Aiming at the challenges of high cost, complex manufacturing processes, and low efficiency in coupling and alignment for microlens arrays on the surface of optoelectronic devices, a fabrication method of self-forming and self-aligning microlens array is proposed. The method forms a microlens array based on the interaction of surface tension, gravity, and air pressure of a liquid transparent packaging medium, aiming at simplifying the manufacturing process of the microlens array on the surface of an optoelectronic device, reducing the cost and improving the production efficiency. Firstly, this paper theoretically analyzes the force on the lower liquid surface after the liquid transparent encapsulation medium drops on the upper surface of the metal film step and discusses the feasibility of forming microlens array by this method. After calculation, the filling factor is improved by 15.4% under the conditions of pixel size of 13 μm, photosensitive area of 10 μm, metal film mesh diameter of 12 μm, and metal step height of 2 μm. Then, experiments are carried out on two kinds of metal meshes with different specifications. Experimental results demonstrate that this method effectively produces microlens arrays with excellent uniformity and has obvious convergence effect on light. Microlens arrays show good performance in metal mesh arrays with apertures of 1 mm and 80 μm and have good application prospects in array photodetectors, displays, optical imaging, optical communication, and other fields.

A description is given of a 15.1-m laser strainmeter installed in Katsiveli (Crimea), designed to record microdisplacements of the earth’s crust based on a device in the frequency range from zero (conditionally) to 1000 Hz with an accuracy of 0.1 nm. The main interference unit of the laser strainmeter is mounted on a concrete base rigidly connected to the upper layer of the earth’s crust, and the corner reflector is located on another concrete base, which is installed on a sand cushion. Between the main interference unit and the corner reflector, the beam of a frequency-stabilized helium–neon laser propagates along a sealed beam guide. A laser pressure variation meter is installed in the sea at a depth of 28 m and at a distance of 580 m from the laser strainmeter. It is designed to record changes in bottom hydrostatic pressure in the frequency range from zero (conditionally) to 1000 Hz with an accuracy of 13.5 mPa. All information obtained by these installations is sent via cable lines to the laboratory room, where, after preliminary processing, it is placed into the experimental database. The conducted synchronous testing of a laser strainmeter and a laser pressure variation meter demonstrated their great potential for studying vibrations and waves in the microseismic range.

A system for probe measurements of a powerful pulse–periodic discharge has been developed, which makes it possible to determine the plasma characteristics at various instants of time. The system consists of hardware and software parts. The hardware includes probes with a sensor unit and a data acquisition board with signal preparation units and a probe power-supply amplifier. To create a controlled probe-voltage source, a high-power high-voltage amplifier with an output-voltage range from –85 to +85 V and a maximum output current of 700 mA has been developed. The measured voltages from the probe, as well as the amplifier input, are connected to the data acquisition board via galvanic-isolation units, which is a prerequisite for precision measurements under conditions of significant interference caused by the power part of the facility. The use of a storage sampling system makes it possible to obtain the current–votage (I-V) characteristics in real time. The software part includes a functionally complete program intended to control the process of recording the I–V characteristics.

To test prototypes of high-power microwave devices, megawatt-class gyrotrons, which are being created at the Institute of Applied Physics (Russian Academy of Sciences), a high-voltage rectangular-pulse generator with a voltage of 100 kV and a current of 50 A was developed and manufactured at the NPP LM Invertor. The generator was put into operation as a part of a test bench for powerful gyrotrons. During tests, its parameters were confirmed, which were provided by new circuit-design solutions implemented when creating the generator. The application of the technique of stepwise (ladder) formation of high-voltage pulses both in the algorithm for controlling high-voltage converter cells and for constructing an insulating structure made it possible to build a highly efficient high-voltage pulse generator.

A method and experimental setup for assessing the mechanical and morphological characteristics of microstructures are presented, which were tested on polymer structures formed using surface-selective laser sintering from biocompatible microparticles. The developed device allows for the measurement of breaking forces in the range from 6 mg to 130 g with an accuracy of up to 3 mg, providing a highly accurate assessment of the mechanical properties of delicate structures. The study included analysis of the internal structure, porosity, thickness distribution, and mechanical strength of the polymer samples. Morphological parameters were obtained using scanning electron microscopy and digital image processing, including adaptive binarization and region-of-interest delineation. The presented method and system can be applied in various fields requiring accurate measurements of tensile strength and elastic and morphological characteristics of samples.

An experimental setup for studying the process of initiating combustion of high-energy materials is considered. The setup combines two combustion initiation options, synchronized with a two-channel visualization system based on a copper bromide vapor laser monitor. The choice is between contact initiation by contacting the test material with a heated electrical conductor or laser initiation using a solid-state laser with a wavelength of 635 nm and fiber optic radiation output. In both initiation modes, the moment of the start of the exposure is synchronized with the moment of the start of recording by the Evercam F 1000-16-C high-speed cameras, which record images in their own glow and images of the laser monitor. Laser monitoring combined with direct video recording allows for simultaneous examination of the sample surface in a selected area and flame spread across the entire sample. When working as part of a laser monitor, both cameras operate as slaves. A special feature of the external synchronization of Evercam cameras is the need to form trains of sync pulses synchronized with the radiation pulses of the brightness amplifier and starting at the moment of the start of the exposure. In this work, synchronization is implemented using fiber optic communication lines and the STM32F103C8T6 microcontroller board. The possibility of using the designed setup for studying the initiation and high-temperature combustion of a thermite mixture based on Al–CuO is shown.

The results of the development and research of semiconductor ionizing-radiation detectors based on p-Si/n-InP heterostructures are presented. The design and technological features of their manufacture are considered, and the results of electrophysical and radiometric measurements are presented. It is shown that the use of a p-Si/n-InP heterojunction provides high sensitivity at low noise and reverse-current levels. The developed heterostructure demonstrates new possibilities for the effective detection under conditions of an increased radiation load, which is especially relevant for experiments at particle accelerators. The manufactured detectors with a large active-region area are designed to detect low-intensity ionizing radiation fluxes, which confirms their prospects for use in nuclear physics, radiation monitoring, and environmental monitoring systems.