Instruments and Experimental Techniques最新文献

A differential amplifier with a high input impedance has been designed and manufactured. Its feature is an additional input for a reference signal that can be summed with the amplifier output signal. As a result, it is possible to detect small changes in the measured value against a significant constant contribution. The gain is 1, 10, or 100. The device is designed as an attachment to the SR830 lock-in amplifier (Standford Research Systems, United States, www.thinkSRS.com), but it can also be used with other devices if an appropriate power source is available.

A method for improving the resolution and response time of adaptive optical systems designed to correct wavefront tilt angles for optical radiation in astronomy, turbulent-atmosphere vision systems, laser-beam control in scanning systems, and optical communication systems is proposed. The method is implemented on a tracking adaptive optical system setup by presetting the Tip-Tilt angle of the additional correcting deflector mirror to a position at which the combined Tip-Tilt angle of both deflectors (stabilizing and additional correcting angles) corresponds to the wavefront tilt angle at the system’s input aperture at the time of recording the next frame. Approaches to calculating the predicted wavefront tilt angles, including the use of an artificial neural network, are considered.

In September–October 2024, an experiment on earthquake registration in the Kuril-Kamchatka subduction zone was conducted using the distributed acoustic sensing (DAS) method. The fiber-optic monitoring system is an independent system consisting of a fiber-optic amplitude vibroacoustic sensor and a fiber-optic cable. The fiber-optic line is deployed in the building of the Institute of  Volcanology and Seismology in Petropavlovsk-Kamchatsky, with the cable securely attached to the building’s foundation to ensure coupling with the building’s structure. The DAS earthquake records were compared with the data from the IVS seismic station. Four tectonic earthquakes that occurred near Petropavlovsk-Kamchatsky were selected for the analysis. It is shown that DAS signals preserve the main features of seismograms, making them suitable for use in seismological kinematic tasks.

The article is devoted to determining the filtration parameters of an oil reservoir by the method of filtration pressure waves. The application of the method in laboratory conditions in the case of rectilinear-parallel filtration is considered. A laboratory installation for studying samples of porous media with an automated laboratory-experiment control system is described. The installation allows one to examine samples up to 145 × 10 × 6 cm³ in size, setting the liquid flow rate, which varies according to a harmonic law with periods of exposure from units of seconds, and measuring pressures at various points in the sample. Based on the time series of the flow rate and pressure obtained, the sample piezoconductivity can be calculated with an error of 3%. The results of an experimental study of sand using the installation and calculation of the piezoconductivity are presented.

The stages of the study of frequency characteristics of detectors based on superconductor-insulator-normal metal-insulator-superconductor (SINIS) structures integrated into various variants of planar antennas in the subterahertz range are considered. The SINIS detector is not a frequency-selective receiver, and it is built into an antenna and optical system in accordance with the required reception band to receive subterahertz radiation. The integration option with broadband log-periodic and narrowband double slot antennas is considered. The results of three-dimensional electromagnetic modeling of the developed antenna designs are presented. Spectra of scale models were produced and measured in the microwave range. Some experimental schemes for measuring the frequency characteristics of SINIS detectors are considered and the results of such measurements are presented.

With the appearance of accelerator-based neutron sources for Boron Neutron Capture Therapy (BNCT), the need arose for an independent system to measure the generated particle flux. For this purpose, Budker Institute of Nuclear Physics (Siberian Branch, Russian Academy of Sciences) developed a fast neutron detector based on a scintillator–optical fiber–silicon photomultiplier detection system. It utilizes three different sensors, allowing for the measurement of neutron flux as well as the estimation of the local dose induced by gamma radiation. The optical signal-detection system based on silicon photomultipliers possesses high quantum efficiency, and the use of a pulse-counting mode for event registration made it possible to achieve an intrinsic noise level of approximately several tens of counts per second. Furthermore, the counting characteristic of the readout electronics is well described by a nonextendable dead time of 24.6 ± 0.1 ns, which allows for the registration of events with minimal miscounting even under high detector load.

A radiometer for monitoring solar activity at 10.7 cm wavelength to predict the near-Earth space state has been developed. The radiometer provides automatic calibration, measurement, visualization, and recording the intensity and polarization of solar radio emission data. Receiving and data acquisition systems’ operating principle is discussed. The software for controlling these systems is described. The radiometer’s measurements and its components’ parameters are presented. Methods for increasing the radiometer sensitivity and stability are proposed and implemented.

Boron neutron capture therapy, a promising treatment for malignant tumors, requires intense neutron beams in the epithermal energy range. Nuclear reactors or particle accelerators generate higher-energy neutrons and slow them to the required energy through elastic and inelastic scattering of neutrons on the atomic nuclei of the moderator material. Neutrons with energies around 10 keV are optimal for treating deeply localized tumors, and a beam shaping assembly with a moderator made of crystalline or pressed magnesium fluoride is used to generate such a neutron beam. For research with cell cultures and laboratory animals, a hydrogen-containing moderator (plexiglass, polyethylene) is used; in this case, the neutron energy spectrum is shifted toward the thermal region. The authors have proposed using a moderator made of polyethylene with a volumetric inclusion of bismuth. This paper presents the results of measurements of the spatial distribution of the intensity of nuclear neutron absorption reactions by boron and the intensity of γ-radiation in a water phantom for three similar moderators made of plexiglass, polyethylene, and polyethylene with volumetric bismuth inclusions. The measurements were conducted using a compact sensor with a pair of injection-molded polystyrene scintillators, one of which is enriched with boron. It is shown that the use of polyethylene with volumetric bismuth inclusions, compared to plexiglass or polyethylene, reduces the unwanted γ-radiation dose while maintaining the neutron flux intensity.

A high-speed exposure shutter for a monochromatic beam of superbright synchrotron radiation beams of generation 4+ sources has been developed. The shutter allows suppressing a monochromatic SR beam with an aperture of up to 3 × 3 mm² by five orders of magnitude in intensity and has an opening/closing response speed of no more than 10 ms. During shutter testing, optimal parameters for the shutter lever operating modes were established. High-speed shooting and video image analysis made it possible to demonstrate the damping of lever oscillations due to subsequent actuator steps when opening/closing pulses are out of phase with the levers’ own oscillations.

A method for correcting dynamical nonlinear distortions introduced by ultrawideband devices in various measuring paths is considered. Devices with an operating frequency range comparable to the center frequency of the range (the absolute frequencies may vary) are considered to be ultrawideband. The method is based on characterizing the device using a set of step responses and replacing this device with an equivalent circuit containing nonlinear resistive and reactive elements. The characteristics of these elements are selected so that this circuit has step responses close to the step responses of the device. Using the equivalent circuit, the device input signals are found from the specified output signals, i.e., the problem of synthesizing an operator with properties inverse to the properties of the object (corrector synthesis) is solved. The used device model functionally corresponds to a nonlinear recursive filter and imposes no restrictions on the shape and bandwidth of the signals under correction. An approach to regularizing the correction procedure to reduce the influence of noise, interference, and systematic errors is considered. Using a baseband pulse power amplifier as an example, it is shown that the static nonlinearity decreases from 16 to 1.4%, and the dynamic nonlinearity is reduced from 44 to 3%.