Instruments and Experimental Techniques最新文献

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.

A universal hardware complex for generating traditional low-temperature plasma and two types of nonthermal atmospheric pressure plasma is presented. The basis of the complex is a low-budget magnetron microwave generator used in microwave ovens for household and industrial purposes. In model experiments with cultures of microorganisms, the biocidal properties of the generated argon nonthermal plasma were confirmed. The sterilizing properties of plasma during the treatment of the surface of the seed material have been established.

A generator of high-power nanosecond pulses consisting of four stages that are switched on in a relay-race mode is described. Each stage contains a storage capacitor with an operating voltage of 8 kV and an assembly of series-connected shock-ionized dynistors. The possibility of switching current pulses with an amplitude of 800 А to a load of 30 Ω a rise time of 4 ns, and a repetition rate of 100 Hz is demonstrated. The prospects for increasing the output voltage and the output energy of the generator are determined.

In this paper, we implement the pulsed current–voltage (PIV) technique for the metal-oxide-semiconductor field-effect transistor (MOSFET) device’s ultrafast characterization based on the OpAmp amplifier OPA818. The latter dropped down the measurement time for a whole MOSFET characteristic to ({{t}_{M}}) = 50 ns as an enhancement. Furthermore, a study concerning the technique’s dependency on measurement time (({{t}_{M}})), channel length ((L)), and channel width ((W)) is accomplished. It is found that the distortion in the technique’s results, labeled as hysteresis, is inversely proportional to measurement time and it increases dramatically with very low values of ({{t}_{M}}). Also, the results show that PIV could have a somehow direct proportionality to channel length, and it is justified by the gate/drain capacitance (({{C}_{{{text{gd}}}}})) effect. On the other hand, the technique shows no dependency on channel width at all. Moreover, as measurements limitations, the results couldn’t record drain currents less than ({{I}_{{{text{ds}}}}}) ≈ 10^–7 A, this makes PIV limited to the study of threshold voltage degradation ((Delta {{V}_{{{text{th}}}}})) only. However, this issue is well discussed and solutions have been proposed.

Adaptive optics (AO) has been widely used to measure and regulate human eye aberrations in real time. However, involuntary eye movement will restrict the working ability of the AO system severely. Thus, we propose a dual-camera three-dimensional (3D) automatic tracking technique for the AO system. In this paper, the basic principle of 3D tracking eye positioning and pupil tracking was introduced. The accuracy and feasibility were verified by practical experiments. The results show that the averaged root mean square error of higher-order aberrations from eight subjects is decreased by 11.5%, and the fluctuation variance is decreased significantly.

Plasma flows with high velocity, density, and energy are widely used in research on the interaction of plasma with materials, modeling of astrophysical processes, development of plasma thrusters and plasma radiation sources, and plasma injection into fusion devices. Electrodynamic plasma guns can be used to generate such flows. This paper describes the design features of a powerful pulsed plasma gun and diagnostic tools for measuring the parameters of the plasma flow generated by it.