Instruments and Experimental Techniques最新文献

A hardware and software complex designed to control the temperature of a permanent magnet of a magnetic resonance imaging system and to protect it from overheating in case of failures of the temperature-control system is described. The complex consists of several digital temperature sensors and a meter-recorder that measures temperatures, registers them in memory, and switches off the temperature-control system in case of overheating. Interaction with the computer is carried out with the help of a computer application that provides the setting of the meter, receiving recorded data, visualizing them in graphical and digital form, and saving them in files. The exchange between the meter and the computer is carried out through the local network using the Wi-Fi interface. The complex can also be used in other similar applications.

Multiple-Input Buck–Boost (MIBB) dc–dc converters receive energy from two or more energy sources that can Deliver Several Outputs of variable power. There are situations in which it is advantageous to use a buck-boost converter, i.e., when there is no guarantee that the input voltage will always be higher or always lower than the output voltage. This happens for example when there is an input voltage in an inverter that makes the interface between the photovoltaic panels or wind generators and the electrical grid. Here, we present a trigger-controlled MIBB converter topology with various input voltage sources and energy diversification of 0–100% of each source, determined by a pre-determined arbitrary value. The full-range linear transfer function of the controller drives the closed-loop MIBB system to operate as a linear single-input buck–boost converter. The response time of the controller is about 400 μs and therefore allows for high-speed real-time control. The intelligent fixed frequency switching strategy overcomes the limitations of present multiple-input converters by switching period sharing. System performance was verified by simulations and an experimental setup with two source inputs. It is shown that the system can be treated as a linear system, controlled by a single parameter—K. As a result, a simple to control MIBB system with a wide input/output range and fast response time is presented.

The results of research works on improvement of technical characteristics of high-current photoelectron multiplier tubes manufactured by FSUE VNIIA used in scintillation detectors for studies of pulsed gamma-neutron radiation are given. The design is described and the results of introduction of new technological processes of photomultiplier manufacturing are presented.

To study the dependence of the equation of state of high-density nuclear matter on the term characterizing the isospin (proton–neutron) asymmetry of nuclear matter, it is necessary to measure azimuthal flow of neutrons as well as azimuthal flow of charged particles from a dense nuclear matter in the nuclear–nuclear collisions. For this purpose, the Institute for Nuclear Research (Russian Academy of Sciences) is developing a new high-granular neutron detector that will be used in the BM@N experiment at the extracted beam of the Nuclotron accelerator at the Joint Institute for Nuclear Research (JINR, Dubna). This detector will identify neutrons and measure their energies in the heavy-ion collisions up to 4 GeV per nucleon. This article presents the results of measurements of the time resolution and light yields of samples of scintillation detectors with sizes 40 × 40 × 25 mm³ that will be used in a neutron detector based on the currently available fast plastic scintillator manufactured by JINR using an EQR15 11-6060D-S photodetector for light readout. For comparison, the results of measurements for a detector of the same size with a EJ-230 fast scintillator and with the same type of photodetector are given. The measurements were made on cosmic muons as well as on the Pakhra electron synchrotron of the Lebedev Physical Institute of the Russian Academy of Sciences located in Troitsk, Moscow.

A broadband receiver of NMR signals on a modern elemental base is described. The developed receiver is made using broadband components, which allows it to be used in a wide frequency range. This allows it to be used to study various nuclei or to use it in magnetic fields of various strengths. This receiver can be used as a part of various devices based on NMR, such as tomographs and relaxometers. To control the receiver, a device based on a programmable logic chip (FPGA) has been developed. The use of programmable logic chips makes it easy to adapt the receiver to work with various control protocols within the same device or in different devices. Specialized software (firmware) has been created for flashing the FPGA.

The use of glass capillaries with an outer diameter at their sharp end of less than 0.3 μm as probes in a manipulator based on an atomic force microscope (AFM) operating in a dynamic full-contact mode is considered. Various aspects of setting up the feedback system in this mode of AFM operation were studied to correctly obtain an image of the topography of the sample under study. Examples are given of the use of capillaries as probes for moving nanowhiskers with a characteristic diameter of 100 nm and hexagonal boron nitride (hBN) flakes with characteristic sizes from units to hundreds of micrometers. The possibility of creating and moving liquid droplets with a volume of less than 100 attoliters has been demonstrated.

This article presents an automated setup for studying the nonlinear optical properties of crystals by single-beam Z-scan with the pulse duration of 5.3 ns. The scheme has been successfully applied to study the nonlinear refractive index of a polycrystalline ZnSe window. The experimental setup and data analysis are described in detail. The measured value of the nonlinear refractive index n₂ was (1.01 ± 0.09) × 10^–11 esu. The developed experimental setup can be used to study the nonlinear optical characteristics of new nonlinear crystals.

A methodology for the fully automated production of optical fibers with a subwavelength diameter has been developed. A detailed description of the implemented automated setup is provided, which enables the production of quartz fibers with a record-breaking small waist diameter of 400 nm, a taper length of up to 100 mm, and a transmission loss level of 0.4 dB at a wavelength of 1550 nm. The reproducibility of the fiber parameters with a desired geometry is ±30%. The proposed methodology for fully automated production allows the significant simplification and standardization of the production of fiber-optic elements of subwavelength diameter for creating efficient coupling elements for optical microresonators with a giant quality factor, as well as for manufacturing subwavelength fibers for optical filtering and absorption spectroscopy applications.

The possibility of cooling a ТеО₂ target during production of radionuclides based on ^123/124I has been investigated. Different cooling methods used in production of radiopharmaceuticals, as well as their advantages and drawbacks, are considered. A new method is proposed for cooling the front side of a solid target (a TeO₂ layer) by a fine-dispersed flow of sprayed water. Experiments have been conducted at the cyclotron of the Tomsk Polytechnic University on the cooling of a TeO₂ target irradiated by an accelerated deuteron beam. As a result, at a water flow rate of 15 mL/min and a spraying plume diameter of 38 mm, the beam thermal energy of 113 W has been dissipated at a target surface temperature of 120−130°C.

In this paper, the Penning ion sources (PIS) characteristics are studied applied to their use in an inertial electrostatic confinement (IEC) system based on a two-electrode spherical chamber. In the IEC chamber with deuterium filling, due to multiple oscillations of ion beams through a gas-plasma target inside the central electrode, a beam-target mechanism for generating neutron radiation is realized. Based on the method for the neutron yield calculating of IEC systems, the requirements for a PIS are formulated to ensure the neutron yield (2.5 MeV) in the range of 10⁶–10⁷ neutr./s. A computational and experimental study of the discharge combustion regimes in the PIS has been carried out depending on the configuration of the external magnetic field and comparison of the currents in the PIS and the currents through the central electrode of the IEC chamber in the pressure range from 0.1 to 10 mTorr. The optimal number of PIS in the considered spherical chamber of the IEC justified.