Instruments and Experimental Techniques最新文献

The paper considers various designs of detectors for the passage of charged microparticles, which can be installed on mass spectrometers in order to record the moment of passage of a microparticle and initiate the measurement process. The largest range of recorded masses and velocities was shown by the detector design, made on the basis of a dielectric base (PLA plastic) using a 3D printer and a nichrome filament.

An apparatus for studying the processes of laser action on various materials, including biological tissue, is described. The system makes it possible to obtain thermograms of the sample surface, conduct high-speed video recording, and record acoustic signals in a wide frequency range during experiments. The system was tested using a pulsed nanosecond high-frequency laser source with a wavelength of 3.03 μm. The samples were exposed to pulses with a duration of 1.5 ns and a frequency of 8 MHz. It is shown that it is possible to use a laser system to obtain incisions on biological tissues of various types without carbonization. The obtained experimental data made it possible to clarify the mechanism of the action of laser radiation on the surface of water-saturated biological tissues.

An independent volumetric glow discharge was experimentally obtained at atmospheric pressure in an argon atmosphere. A volumetric glow discharge is realized in an electrode system consisting of a thin metal wire and a metal grid with a dielectric barrier and is ignited using an auxiliary discharge, a low-current surface discharge initiated at the end of a glass tube along the dielectric surface between the pointed cathode and a cylindrical metal anode.

A method for recording the spatial distribution of radiation scattered from laser plasma in a wide angular range, up to 4π, using preexposed and developed photographic paper is proposed. This method makes it possible to obtain a radiation pattern of scattered radiation with a sufficiently high spatial and angular resolution. By calibrating the sensitivity of photographic paper, one can quantify the energy of scattered radiation in various directions and determine the integral value of the energy loss due to scattering in a wide spectral range from UV to IR.

A method for detecting changes in the length of an optical cavity is proposed for fiber-optic sensors based on the Fabry–Perot interferometer scheme. The possibility of detecting oscillations of the resonator length at the subnanometer level in the frequency band 1.5–300 kHz is shown. The sensitivity was 0.3 nm in standard deviation. The proposed scheme makes it possible to reliably distinguish high-frequency oscillations against the background of slow drifts of the sensor length caused by temperature fluctuations or deformations.

A simple and effective technique for express diagnostics of materials, which allows for the most efficient preparation of samples, the actual measurements, and obtaining data on material parameters, in particular, on the dispersion of the permittivity, is proposed. An express method for impedance spectroscopy of small samples at frequencies from 20 kHz to 1 GHz has been developed on the basis of a vector network analyzer using a conical coaxial measuring cell and adapters for connecting two-pole objects to the coaxial input of the device. The measuring cell is designed for disk samples with a diameter of up to 6 mm with a maximum volume of up to 0.1 cm³ as well as for samples in the form of rectangular plates that can be inscribed in a circle of the same diameter. Adapters also make it possible to connect two-terminal networks in the form of concentrated hinged or surface-mounted elements. In contrast to measurements in a coaxial path, the proposed technique does not require an accurate connecting transverse dimension, which allows for prompt sample preparation. The issues of determining the frequency range in which the measurement error does not exceed the allowable value are considered. A method is proposed for increasing the upper limit of the operating frequency of the measuring cell with the test sample using additional calibration. The developed program for controlling the processes of standard and additional calibration and the process of measurements in a certain frequency range, at which the measurement error does not exceed the permissible value, makes it possible to obtain the values of resistance, capacitance, inductance, and other electrical characteristics of the measuring cell with the sample under study within a few seconds.

New possibilities for the mode of detecting backscattered electrons in a scanning electron microscope (SEM) are presented. The technique for determining the chemical composition of the probed area of the sample using the precalibrated scale of the SEM’s gray screen has been further developed. Simple relationships are presented for practical application in finding the thicknesses of thin films on a massive substrate. The parameters of the double layer of the film nanostructure on the substrate are determined, that is, depth and thickness of subsurface fragments of the microobject. A technique is proposed for measuring the surface potential of negatively charged dielectric samples upon irradiation with medium-energy electrons.

A new method for processing spectral-domain optical coherence tomography signals, which is designed to effectively suppress motion artifacts under conditions of large probing depths, is described. The features of this method made it possible to use it as part of an otoscopic system of spectral-domain optical coherence tomography, which ensured high quality of real-time imaging.

Deployment of the deep-sea neutrino telescope Baikal-GVD continues in Lake Baikal. By April 2022, ten telescope clusters, which include 2880 optical modules, were put into operation. One of the urgent tasks of the Baikal project is to study the possibility of increasing the detection efficiency of the detector based on the experience of its operation and the results obtained with other neutrino telescopes in recent years. In this paper, the authors consider a variant of optimizing the telescope configuration by installing an additional string of optical modules between the detector clusters (external string). An experimental version of the external garland was installed in Lake Baikal in April 2022. The paper presents the results from calculations of the efficiency of registration of neutrino events for a new setup configuration, the technical implementation of the system for recording and collecting data from the external garland, and the first results of its full-scale tests in Lake Baikal.