Instruments and Experimental Techniques最新文献

The multicomponent gas analyzer has a wide range of applications, such as environmental monitoring, chemical reaction and industrial process control, accident prevention, exploration in the oil and gas industries, and biomedicine. Laser photoacoustic spectroscopy is the universal method for analyzing gaseous impurities due to its high selectivity, sensitivity, and fast response. This paper presents an automated gas analysis system based on the combined optical parametric oscillators tuning from 2.5 to 10.8 µm. The full width at half maximum of the spectral line is approximately 5.5 ± 0.5 cm^–1 in the range from 2.5 to 4.5 μm and approximately 2 ± 0.5 cm^–1 in the range from 4.5 to 10.8 μm. Using software installed on the control computer, the controller performs all necessary operations, including pumping, analysis, and removal of gas samples in the measuring complex. The paper presents experimentally recorded absorption spectra of gas mixtures of CO, CO₂, and CH₄ obtained using a differential photoacoustic detector.

The experiment on the placement of side acoustic steel screens at different heights from the radiating surface is described. The radiation patterns (RPs) have been recorded. The width of the main lobe of the RP in a vertical plane at a level of 0.707 is analyzed as a function of the heights at which the side acoustic shields are located.

To measure the spatial distribution of the magnetic field, both single Hall sensors and arrays of Hall sensors are used. In most cases, a one-dimensional ruler is sufficient. The finished device is called a measuring carriage. The rest of the article describes the first stage of its creation. This article consists in Hall sensor rejection, during which the sensors operate under extreme operating conditions (with increased electrical and thermal loads). During this so-called accelerated aging, the changes in the residual stress values, temperature coefficients, nonlinearity, and divergence of the sensitivity coefficient were monitored. This study can serve as a methodological guide in determining the selection criteria for Hall sensors for precision measuring systems. The need for aging sensors was shown to stabilize their long-term characteristics. In addition, the process of rejecting sensors according to the parameters of interest is described.

This article uses polydimethylsiloxane (PDMS) to package an improved fiber Bragg grating (FBG) temperature sensor. Unlike the structure of PDMS completely enveloping fiber gratings, we utilize microfluidic processing technology to construct a microchannel with a diameter of 150 μm in the area of the fiber gratings. It eliminates the thermal stress on the fiber grating in the radial direction. Through the force analysis of the fiber gratings in the packaged sensor, it can be found that eliminating the radial thermal stress is conducive to improving the axial coefficient of thermal expansion of the fiber gratings. The temperature sensing characteristics of this structure are verified by simulation and experiment. Both theoretical and experimental results have shown that this structure can effectively improve the temperature sensitivity of the sensor. In the experiment, the temperature sensitivity of the packaged sensor is 3.5 times higher than that of the standard fiber gratings. The temperature sensitivity of the sensor is 37.6 pm/°C. It is simple to manufacture, does not pollute the environment, and can accurately monitor the temperature of the complex environment. Therefore, it is an ideal model for temperature monitoring in complex environments such as the ocean and mine.

A high voltage electric-discharge device is considered that provides the production of steel, aluminum, and silicon particles with a size of less than 100 nm from granules placed in a chamber with running deionized water. The possibilities of significantly increasing the power of the developed device have been determined.

A short external cavity (EC) providing a single frequency lasing of quantum-well diode lasers with broad optical gain profiles has been developed. A feature of the proposed EC is the use of a resonant reflector formed by two thin (with thickness of approximately 100 µm) cover glasses as a return mirror. The HL8338MG laser equipped with a similar short EC made it possible to demonstrate the continuous optical frequency tuning within 100 GHz and discrete wavelength tuning in the 12.3 nm range with an output power of approximately 20 mW. The applicability of such a tunable diode laser source for gas spectroscopy was confirmed by the observation of three krypton absorption lines near 829 nm in a low-pressure radio frequency discharge.

The possibility of using modern energy-intensive storage devices based on supercapacitors in relation to the tasks of powering magnetic systems of high-power microwave generators based on a relativistic backward wave tube (BWT) is described. Magnetic systems of such generators consist of a two-section solenoid. During the operation of the generator, a current of up to 700 A flows through the windings of a solenoid for few seconds. The magnetic system is powered from a capacitive storage device based on supercapacitor modules through step-down current regulators. Current stabilization is carried out by increasing the duration of the open state of the switches as the storage device is discharged. The control system contains a microprocessor that controls the power switches of current regulators as well as the management of the drive charging processes and interaction with peripheral devices. The work presents all the necessary formulas for calculating the parameters of the current regulator and estimating the storage capacity and its energy characteristics. Also, two variations for the implementation of similar power supplies are presented: the maximum output power of the first one is 280 kW with an output current duration of up to 1.5 s, and the maximum output power of the second one is 90 kW with an output current duration of up to 2.5 s.

A proportional-integral-derivative-based (PID based) sliding mode control (SMC) was applied to the linear stage driven by a constraint-tuning modified-mode (CTMM) ultrasonic actuator. Based upon the driving variation of voltage amplitude and the preload on the CTMM ultrasonic actuator, nonlinear phenomena, such as frequencies shifting in electromechanical resonance and the dead zone in moving response, could be suppressed almost completely by the PID based SMC controller with output biases. Using system identification technique, an approximate second-order model of the linear stage could be obtained for the equivalent control term of the PID based SMC controller. Through an estimated model error, the design of the switching control term was used to compensate for the shifting property of resonant frequencies under electromechanical coupling. A target-command-shaping function matched the responding speed of the system during tracking experiments. Experimental results demonstrate that the SMC controller has the capacity for noise rejection to control the slider’s position in bilateral tracking motions. Its resolution is sufficient to approach micrometer-level accuracy.

A compact emitter of a relatively simple design with argon filling has been developed, which can be used to create VUV and UV excilamps. Its characteristics were investigated. To increase the radiation power on the second continuum of argon dimers (λ ≈ 126 nm), a method based on gas flow through the discharge region was used. At an excitation pulse repetition rate of 96 kHz, the radiation power density at λ ≈ 126 nm behind the output window made of MgF₂ greater than 5 mW/cm² was obtained. It is shown that argon flow at a rate of 0.5–1 L/s through the discharge region makes it possible to stabilize the average power of VUV radiation at a level no worse than 2%.

This article describes the design of the HGND detector (High Granular Neutron Detector) for measuring azimuthal neutron fluxes in the range from 300 to 4000 MeV as well as heavy ions formed in nucleus-nucleus collisions at energies up to 4 AGeV in the BM@N (Baryonic Matter at Nuclotron) experiment on the extracted beam of the JINR Nuclotron, Dubna. The detector consists of 16 layers of plastic scintillation detectors having a cellular structure with copper absorption plates between the layers. The results of measuring the time resolution of scintillation cells using silicon photodetectors are presented. The proposed electronics circuit for reading signals from scintillation cells is described. The results of modeling the acceptance of a neutron detector, the efficiency of neutron detection, the neutron energy resolution, and an estimate of the neutron count rates for the Bi + Bi reaction at an energy of 3 AGeV are presented.