Instruments and Experimental Techniques最新文献

A hybrid muon hodoscope for muonography of large-scale objects has been created in the Scientific and Educational Centre NEVOD (MEPhI) with the participation of the National Research Center “KI”–IHEP. The multichannel detecting system of the hodoscope consists of a scintillation strip detector and a detector on drift tubes and is designed to detect tracks of charged particles, mainly muons, flying through the detector volume. The drift tube detector is an important recording element of the muon hodoscope, providing high angular and spatial accuracy of muon track reconstruction. The article describes the design of the drift tube detector, the principles of operation of the readout electronics, and also provides the main technical characteristics.

The schematic diagram and design of an electrostatic lens for correction and additional focusing of a beam coming out of a magnetron-type ion source are described. A drawing of such a lens is presented.

Optical time domain reflectometer (OTDR) is the most basic and widely used equipment in optical fiber detection. Its performance and trace analysis ability play a decisive role in the maintenance of optical fiber. Traditional OTDR event detection methods rely on manual definition of pulse characteristics, require professional prior knowledge, and require high signal-to-noise ratio. The traditional preprocessing methods such as smoothing and denoising have some actual signal characteristics weakened or even disappeared. UNet is the most classical U-structured network model applied to medical image segmentation. It can learn a very robust model for edge extraction by using a small amount of data. Inspired by this, we propose the first OTDR event detection method based on the improved 1D UNet, which makes full use of the convolution neural network to automatically extract signal features. It can be applied to small sample data sets and it can accurately identify multiple types of events such as power injection, reflection, drop, end and echo events, with an average detection rate of 90%. Compared with the EXFO FastReporter software widely used in the industry, our method shows a stronger ability to resist noise interference, and the detection of echo events in high noise areas reaches 89%.

A regular monodisperse flow of spherical microtargets of solid hydrogen or deuterium with a variable diameter of several tens of micrometers and a frequency from several tens to several hundreds of kilohertz is in demand as internal targets in physical experiments at accelerators. The paper is devoted to the modification and launching of a prototype cryogenic corpuscular hydrogen target in which the gas entering the facility is transformed into a flow of spherical microtargets. Processes of cryogenic cooling and liquefaction of the gas, formation of a liquid microjet, and its controlled monodisperse disintegration into equal-sized drops are realized in the target, and they are followed by freezing of the drops and formation of microtargets upon injection into vacuum. The target prototype is composed of the cryogenic, vacuum, and gas systems as well as the systems for control and optical diagnostics of microtarget parameters. The modified target prototype provided monodisperse regimes of generation of microtargets with a diameter of 20–50 μm at a generation frequency of 260–465 kHz.

The design and parameters of scintillation detectors of Compton polarimeters for measuring photons formed during the annihilation of electron-positron pairs at rest are considered. The discussed setup makes it possible to measure and compare the polarization correlations of scattered annihilation photons in these two quantum states. The amplitude parameters of scatterers and scattered photon detectors obtained from preliminary tests of these detectors using radioactive gamma sources, as well as in the process of collecting experimental data, are given. The possibility of measuring and comparing the polarization correlations of scattered annihilation photons is shown.

A diagnostic system has been developed on the gas dynamic trap (GDT) for detecting deuterium fusion products as well as X rays and γ rays produced by interactions of superheated electrons with structural elements of GDT and by capture of neutrons by nuclei of surrounding materials. The diagnostic system consists of the following three subsystems. The first subsystem is used to measure the longitudinal intensity profile of the dd-fusion reaction. It is based on diode detectors of 3.02-MeV protons and preamplifiers capable of operating with large-area diodes mounted in specially developed detector modules. The detectors are located inside the vacuum chamber of the GDT; they operate in the counting mode, which allows absolute measurements of the reaction-product flux with a time resolution of ~100 μs. Such detectors were created taking into account the operating experience of a proton detector based on an experimental diode in the GDT experiment. The second subsystem is composed of detectors developed earlier on the basis of SPM-5 plastic scintillator and a photomultiplier tube (PMT). These detectors are operated in the current mode and are intended to measure the neutron-generation intensity with a time resolution as high as 25 μs. These detectors are used jointly with the proton detectors in experiments with the additional heating to determine the contribution of γ rays and hard X rays. The third subsystem is a new neutron and γ-ray spectrometer based on a stilbene scintillator and a PMT, which was used for the first time in the experiment with deuterium plasma at the GDT facility. The detector is capable of separating particles of different types, in particular, under the operating conditions of the facility when superheated electrons are generated.

The temperature effect plays an important role in the response function and efficiency of detectors. In this study, the behavior of doped NaI (Tl) and plastic scintillators was evaluated and compared with temperature changes, in a similar condition, for the first time. The detection system uses an experimental setup consisting of a ⁶⁰Co source, NaI (Tl) detector, and a plastic scintillation detector. The results show that the recorded count rates from NaI (Tl) detector have a direct relation with temperature and lead to a 0.15%/°C error in the count rate. But in the same condition, the acquired count rates from the plastic scintillator detector were reduced with temperature increasing with a 0.57%/°C error in the count rate (inverse relation). Also, in this work, Linear and second-order polynomial regression were implemented on the recorded count rates from scintillators to compensate temperature effect. Finally, the acquired results were evaluated using the relative error (%) and diagram slope which expressed the superiority of the polynomial regression. Using this correction technique, the count rate changes reached to least and are stable with temperature fluctuations. The results of this research can be suitable for the industrial application of NaI (Tl) and plastic scintillators in level gauging, thickness gauging, and other nuclear gauging systems.

Space optical clock is an important device for future space science experiments. Inevitably, the micro-vibration level in the order of micro-g (μg) is required for ultra-stable optical reference cavity of space optical clock. However, the existing research on active vibration isolators of space optical clock is still in the laboratory development stage, and their vibration isolation control algorithms still rely on high-performance commercial real-time controllers, making it difficult to meet the application requirements for isolators of space optical clock. On the basis of the previous work, this paper describes the development an active vibration isolator that meets the experimental requirements of the space optical clock. Based on the DSP embedded vibration isolation controller, an anti-saturation control algorithm is designed, which solves the problems of high order of robust controllers, large computing resources and difficult parameter debugging. The active vibration isolation experimental system is further developed, and the experimental results validate the effectiveness of the developed active vibration isolator and anti-saturation control algorithm.

The article is devoted to the study of a methane leak detector based on absorption spectroscopy. An LED matrix with a wavelength of ~3.3 μm was used as a radiation source, where one of the methane absorption lines is located. The system is temperature stabilized. A threshold sensitivity of approximately 60 ppm CH₄ was obtained.

The equipment for studying the formation of jets of volatile liquids in a rarefied environment is described. The equipment was created on the basis of a gas-dynamic installation with high pumping capacity designed for the study of supersonic gas flows. The description and results of testing of equipment and verification of photo and video recording techniques of ethanol nozzle outflow for studying the shape and structure of liquid jets under various conditions under long flow conditions from submillimeter diameter nozzles are given.