


卷 61, 编号 5 (2018)
- 年: 2018
- 文章: 24
- URL: https://bakhtiniada.ru/0020-4412/issue/view/9743
Nuclear Experimental Technique
A Neutron Spectrometer for Experiments with Radioactive Beams on the ACCULINNA-2 Fragment Separator
摘要
A neutron spectrometer based on stilbene crystals has been developed by the Flerov Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research (Dubna, Russia). The timing resolution is determined as a function of the signal amplitude (σT = 0.18 ns at an amplitude of 1 MeV in the electron equivalent). The measured energy resolution of the detecting modules for γ rays is σE/E = 4.5% at E = 1 MeV. The quality of the n–γ discrimination is investigated. It is shown that reliable discrimination is possible, beginning with a deposited energy of 100 keV in the electron equivalent, which corresponds to the kinetic energy of recoil protons of ∼700 keV. The neutron spectrometer helps to significantly expand the experimental capabilities and to carry out correlation experiments with radioactive beams on the ACCULINNA-2 fragment separator at a new level of quality.



Use of Large-Area Photodiodes for Improving the Characteristics of an Electromagnetic Calorimeter Based on Lead Tungstate Crystals
摘要
It is shown that an increase in the area of photodetectors allows the PHOS electromagnetic calorimeter of the ALICE experiment to operate at room temperature with better spectrometric characteristics. The linearity of the calorimeter response has been investigated in the 1–110 GeV energy range using both Hamamatsu S8664-1010 avalanche photodiodes with a large area (10 × 10 mm2) and arrays of MPPC Hamamatsu S12572-015C silicon photomultipliers with a sensitive area of 6 × 6 mm2. The calorimeter based on avalanche photodiodes is linear in the energy range under investigation compared to a calorimeter composed of silicon-photomultiplier arrays.



A Tracker Prototype Based on Cathode Straw Tubes
摘要
A prototype of a 2D detector based on specially designed straw tubes with cathode data readout has been developed and tested. This detector exhibits comparable accuracies in measuring radial and longitudinal coordinates. Its rate capability is similar to the capabilities of traditional detectors whose tubes are smaller by half in diameter.



A Cherenkov Water Calorimeter Based on Quasi-Spherical Modules
摘要
A description of the detection and data-acquisition systems of the Cherenkov water calorimeter of the NEVOD Experimental Complex, which is a unique scientific facility located on the Earth’s surface, is presented. In the development of these systems, a solution is sought to the problem of measuring the energy of cascade showers initiated by single muons and the energy deposited by high-multiplicity muon bundles in a wide energy range.



Computer Simulation of a Transition-Radiation Detector Prototype Based on Straw Proportional Chambers
摘要
A prototype of a transition radiation detector based on straw proportional chambers has been tested at the CERN SPS accelerator beams. A detailed Monte Carlo simulation program has been developed to describe the results obtained during these measurements. Some data obtained in beam tests and their comparison with simulation results are presented.



Detectors on the Basis of High-Purity Epitaxial GaAs Layers for Spectrometry of X and Gamma Rays
摘要
The characteristics of detectors of soft-X and γ rays based on high-purity epitaxial GaAs layers are discussed. The characteristics of detectors with different rectifying contacts are compared, that is, those with a Schottky barrier and a p–n junction. The spectral characteristics of the manufactured detectors that were obtained under the irradiation by 57Co and 241Am sources at different bias voltages and in a photovoltaic mode and the simulation results using the Geant 3.21 software package are presented.



The Calibration Telescope System of the NEVOD Cherenkov Water Detector
摘要
The calibration telescope system of the NEVOD Cherenkov water detector is described. Scintillation counters are used in the setup as detecting elements. The detection system is equipped with logical and amplitude channels and provides the calibration of the Cherenkov water detector. It can also be used to investigate the electron and muon components of an extensive air shower. A method for amplitude calibration of the scintillation counters is described, with which it is possible to estimate the number of detected charged particles. The results for the 1.5-year operation of the setup as a detector of extensive air showers are presented.



Determination of the 14C Concentration in a Liquid Scintillator for a Neutrino Detector
摘要
A setup has been developed for studying ultralow 14C concentrations in liquid scintillator samples for a large neutrino detector. The setup is located at the low-background underground laboratory of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) at a depth of 4900 m of water equivalent. The 14C concentrations in a liquid scintillator based on linear alkyl benzene, the background counting rates, and the spectra of particle energies deposited in the technological scintillator sample have been measured. The ratio 14C/12C = (1.41 ± 0.12) × 10–16 has been obtained. A model of the γ-ray background has been developed, with which it is possible to extract the energy spectrum of 14C and reduce the systematic uncertainty of measurements.



Application of Computers in Experiments
The Telemetry, Command, and Precision Control System for the GRIS-FKI-1 Space Experiment Onboard the International Space Station
摘要
The telemetry, command, and precision control system of the GRIS (γ- and X-ray radiations of the Sun) instrument for the future GRIS-FKI-1 space experiment is described. This experiment is aimed at investigating nonstationary hard X- and γ-ray fluxes from the Sun onboard the International Space Station. Compared to the resources provided by onboard systems, the set of proposed hardware greatly expands the capabilities of the instrument in the acquisition of service data and control, including the precision control, of the detectors characteristics. The system also helps to improve the thermal conditions and calibrate the spectrometric detectors of the instrument during an experiment.



A Single-Photon Detector Module
摘要
A module for recording single-photon pulses is described. It is able to reliably operate in the mode of single-photon counting at a wavelength of 1550 nm (the minimum attenuation in quartz fibers). For this purpose, unique avalanche photodetectors (APDs) based on InGaAs/InP heterostructures with the three-stage cooling to temperatures of –50°C via Peltier elements are used during reception. Test measurements of the level of noise counts, including both dark pulses and afterpulses, have been performed using the developed testing system. The dependences of the recorded noise counts on the duration of gate pulses have been obtained. The nonlinear character of these dependences is evidence of the difference in the contributions of the afterpulsing effect and the dark pulses of the APDs to the noise counts. At short durations of the gate pulses, the major contribution to the noise counts is made by dark pulses of the APDs.



Electronics and Radio Engineering
A High-Power Semiconductor Generator for an Atomic Injector
摘要
An atomic injector with a beam power of 1 MW for heating plasma in the TCV tokamak (Lausanne, Switzerland) by a beam of neutral atoms was developed and put into operation in 2015–2016 at the Budker Institute of Nuclear Physics SB RAS (Novosibirsk). Plasma in the injector is formed in a plasma emitter by a high-frequency magnetic field, which is created by a high-power semiconductor generator with an output power of 40 kW at a frequency of 4 MHz. The facility operates in the pulse mode with a pulse duration of 2 s and a pause of 5 min. The generator is manufactured in the form of a modular system consisting of 16 identical generator modules, whose high-frequency power is summed, control modules, and a power-supply source. The generator allows modulation of the output power in the range of 30–100% by changing the power-supply voltage. The general structure of the generator and its elements and the results of its commissioning are presented.



Certain Features of the Development, Modeling, and Tuning of Microwave Filters Based on Cavity Resonators for Use in Microwave Modules on the Basis of Printed-Circuit Boards
摘要
The theoretical dependences and physical regularities on which the concept of cavity resonators is based are described. The process of modeling a number of filters and the results are described in detail. The filter assembly and tuning process is described as well. The results for the model and an actual filter are compared and analyzed.



A Family of Precision Power Supplies for Corrector Magnets of the European X-Ray Free-Electron Laser
摘要
Six types of precision stabilized-current sources (power supplies) have been developed to correct the parameters of the electron beam at the European X-ray Free-Electron Laser. Power supplies are designed to feed the windings of corrector magnets with a direct current of up to 10 A. Based on the stability requirements of the electron beam, the permissible output current instability should be 10–5 or less. All power supplies must satisfy the requirements of electromagnetic compatibility with the electronics of the free-electron laser. The circuit and design features of the power supplies are described and the test results are presented



General Experimental Techniques
Use of a Wire Scanner for Measuring a Negative Hydrogen Ion Beam Injected in a Tandem Accelerator with Vacuum Insulation
摘要
A modified wire scanner and a new methodical approach were used to measure the profile, current, and phase portrait of a negative hydrogen ion beam injected into a tandem accelerator with vacuum insulation. The effect of the space charge and spherical aberration of the focusing lenses on the negative hydrogen ion beam is revealed. Recommendations are given, whose implementation will make it possible to increase the current of the proton beam from 5 to 10 mA in the accelerator, which is sufficient for boron neutron capture therapy of malignant tumors.



In Situ Surface Imaging Through a Transparent Diamond Tip
摘要
A new approach to the design of transparent diamond indenters is proposed, which allows one to obtain a full optical image of the investigated area of the sample surface, including images directly during measurements by applying the indentation and scratching methods. In this case, it is not required to use immersion liquids that fill the region between the sample and the indenter. The measured area is observed with an optical microscope with illumination through an objective lens. Using an indenter in the form of a trihedral Berkovich pyramid, images of the surface of a test structure and the residual indentation are reconstructed and an image of the surface during its deformation under the application of a load to the indenter is obtained.



Physical Instruments for Ecology, Medicine, and Biology
The MONICA Experiment for Investigating the Ion Composition of Solar Cosmic Rays
摘要
The MONICA satellite-based experiment is described. In this experiment, fluxes of cosmic-ray ions from H to Ni are investigated near the Earth in the energy range of 10–300 MeV/nucleon. The main scientific objectives of the MONICA experiment are to measure the ion and isotope compositions and the energy spectra of solar cosmic rays for individual solar events and to study the evolution of these characteristics over time. The MONICA experiment will help to investigate the ion and isotope composition of the anomalous component of cosmic rays, galactic cosmic rays, and nuclear fluxes in the Earth’s radiation belt. Observations of ion fluxes will be carried out using the MONICA high-aperture multilayer semiconductor spectrometer–telescope installed on board a spacecraft with a low-Earth circular polar orbit at a height of approximately 600 km. This orbit will make it possible to perform the method for measuring the charge of ions with energies above 10 MeV/nucleon, which is based on the use of the Earth’s magnetic field as a particle- charge separator. The geometric factor of the instrument is 100 cm2 sr and the angular resolution is 1°.



Measuring the Beam Density of Accelerated 12C Ions Using Computer Analysis of Microscopic Photographic Images of Etched CR-39 Plastic Surfaces
摘要
The numbers of detected ions and the beam density dispersions at different depths of plate locations that also cover the Bragg peak region were determined by automatically searching for etched micropores in photographs of surfaces of CR-39 plastic plates exposed to 12C ions with an energy of 216 MeV/amu in a chamber for radiobiological investigations at the TWAC–ITEP accelerator–accumulator facility. A computer method for seeking etched micropores along latent ion tracks in an exposed plastic is described. Frequency distributions of detected ions over microscopic areas of each surface for eight plates have been obtained and compared using a Gaussian function.



A Sensor for Tuning Highly Homogeneous Magnetic Fields
摘要
The information on the spatial distribution of a magnetic field in a rather large volume is needed, for example, in magnetic-resonance tomography, when it is important to have a uniform magnetic field in the working region of a tomograph. The stages of the optimization of a magnetic-field sensor, which is used to adjust the magnetic-field homogeneity, are described. These stages are aimed at a decrease in the measurement errors that are associated with the parallel registration of several harmonics, which constitute the magnetic field. The results of calculations on the mathematical modeling of various configurations of the magnetic- field-uniformity sensor and the practical implementation of the chosen variant are presented.



A Method and a Device Prototype for Noninvasive Measurements of Blood Perfusion in a Tissue
摘要
Noncoherent fluctuation spectroscopy (NFS) is described as an optical method for measuring the tissue blood perfusion. This method is based on the registration of low-frequency fluctuations of a backscattered signal from a tissue in the frequency range of 0–20 Hz. It allows the assessment of the blood-flow intensity in small blood vessels of the skin by calculating an integral parameter, the perfusion index, which is similar to that in the laser Doppler flowmetry (LDF) method. A device prototype in which LEDs at wavelengths of 568 and 808 nm are used in a miniature optical head was developed. The device makes it possible to perform diagnostics during the subject’s motion via the use of LED light sources. It is shown that the NFS signal is comparable with the LDF signal. Thus, the NFS method can serve as an inexpensive alternative to the LDF method.



Laboratory Techniques
A Controlled Magnetic Clamp
摘要
A clamp for establishing a thermal contact between cryostat components in a vacuum is described. The contact is established by pressing heat conductors to each other using a permanent magnet and is broken or established by applying a current pulse of the required polarity to the winding around an iron magnetic core. The device is held in the open state by a second permanent magnet. Through the pressed contacts, a copper block with a mass of ∼600 g is cooled in the vacuum from the liquid-nitrogen temperature to the liquid- helium temperature within 4–5 h.



An Automated Setup for Depositing Sensitive Coatings on the Surfaces of Solid-State Sensors
摘要
The design of an automated setup for depositing functional polymers on the surfaces of gas-sensitive solid-state sensors is described. It is based on the irrigation method, which is the most effective technique. The results of experiments on the deposition of films of functional polymers on the surface of a sensor on surface acoustic waves with an operating frequency of 170 MHz are presented. It is shown that the use of the developed equipment makes it possible to reduce the spread of the characteristics of the obtained sensors, in particular, in the initial mass load from 9.9 to 2.8%, and also to improve the static and dynamic characteristics of the sensors.



A Technique for Registering Wave and Vortex Motions on a Liquid Surface
摘要
A technique that allows simultaneous measurements of vortex and wave motions of fluids is described. To record the vortex motion, a liquid surface is decorated with light particles of PA-12 polyamide with an average diameter of 30 μm and video filming of the motion of these particles is performed. The wave motion on the water surface is recorded using an improved method that we proposed earlier for spatial recording of waves on the surface of a transparent liquid; this involves video filming of a contrast stencil lying on the bottom of an experimental pool. The distortion of the video image of the stencil through the transparent liquid layer allows the vertical velocity component to be reconstructed.



A Magnetic Resonance Force Microscope Based on the Solver-HV Probe Complex
摘要
The design and operation principles of a magnetic resonance force microscope (MRFM) that has been developed on the basis of the Solver HV vacuum scanning probe microscope are described. This device is intended to study local microwave properties of ferromagnetic micro- and nanostructures in the frequency range of 0.1–20 GHz and in an external magnetic field as high as 0.35 T.



A Calorimeter Based on Peltier Modules
摘要
A two-chamber calorimeter with industrial TEC1-12706 Peltier modules used as heat-flow sensors and heating elements is described. The measured temperature dependence of the volt–watt sensitivity in the temperature range from –180 to 50°С is presented. The features of the measuring technique are described. The measured temperature dependence of the specific heat of ice is shown.


