Instruments and Experimental Techniques最新文献

The first results from the development of previously unknown tellurium-loaded plastic scintillators based on polystyrene, poly(methyl methacrylate), and their copolymers for detectors for the search and study of neutrinoless double beta decay are reported herein. A complex compound of diphenyltellurium oxide with di-(2-ethylhexyl)phosphoric acid and diphenyltellurium di-2-ethylhexanoate were used as tellurium-containing additives. The conditions for obtaining samples have been described and their light yield and transparency has been characterized.

An oxygen-free copper-based cell has been designed to perform X-ray scattering experiments from the solid-supported lipid membranes immersed in water. This cell can be used to investigate the structural changes in the membrane depending on the composition of the lipids, the effects of temperatures, and the changes in arrangements of the lipids in the membrane on the addition of the external molecules. The design of the cell has been optimized to get a good signal-to-noise ratio (SNR) for the measurements of  X-ray reflectivity and grazing incidence diffraction by controlling the X-ray path within the liquid in the cell and easy operation for variable liquid temperature. This very low-cost temperature-controlled setup, developed in our laboratory, can perform in situ X-ray measurements at various temperature ranges—starting from around 4°C up to 70°C which is very relevant to study the phase transition temperature of the lipids constituting the cell membranes. The detailed mechanical design of the cell and electrical control mechanism of the temperature of the liquid inside the cell has been discussed here. One such X-ray reflectivity measurement is shown here to express the capability of the cell for the study of the solid-supported bilayer sample composed of dipalmitoyl phosphocholine lipid at two different temperatures, below its phase transition temperature.

The results of comparative studies of generators of high-power submicrosecond rectangular pulses are presented. The switch in these generators is made in the form of a transistor block with a transformer control circuit. A block consisting of ten transistors connected in series is described, which is able to commutate into a load of 150 Ω rectangular current pulses with an amplitude of 50 A, a duration of up to 1 μs, and rise and fall times of less than 50 ns at a repetition rate of 2 kHz. The possibility of increasing the switched power by increasing the power voltage up to tens of kilovolts is determined.

A technique is proposed for reconstructing the electron temperature profile under conditions when the integral absorption coefficient of electron cyclotron emission (ECE) is less than unity. Numerical simulations of plasma ECE were performed for the L-2M stellarator in the ohmic heating regime. It is shown that the radiation temperature profiles recovered from the ECE diagnostics data in the ohmic heating regime require considerable correction. The profile width turns out to be smaller than the width of the true temperature profile, and the on-axis plasma temperature is underestimated by ~30%. A new method is proposed for the relative calibration of ECE diagnostics channels in the ohmic heating regime. The resulting calibration coefficients can be used to measure the plasma temperature in the electron cyclotron resonance heating regime.

A channel for measuring the magnetic flux density based on four integrated Hall-effect magnetic sensors (IHMSs) is described. Built-in thermal compensation and dynamic offset cancellation circuits of IHMSs do not eliminate the sensor’s magnetic sensitivity drift due to the thermomechanical packaging stresses that causes an output-voltage offset. The placement of the sensors in a thermostatically controlled cell, as well as the design and circuit solutions related to the spatial orientation of the sensors relative to the magnetic induction vector and to the IHMS output voltage processing algorithm, made it possible to minimize the instability and increase the signal-to-noise ratio of the channel’s ADC input voltage. The design and operation of the hardware–software-based PI controller that regulates the thermostatted cell temperature are considered. The developed channel is used to measure the magnetic-field flux density of the magnetic analyzer of the mass-spectrometric system for isotopic analysis of noble gases and provides the following specifications: the measurement range is ±512 mT; the bandwidth is 0–4 Hz; the noise-free code resolution of the channel is 16.3 bits; the peak-to-peak value of the equivalent input magnetic noise in the bandwidth is 0.012 mT; and the equivalent input long-term drift of measurements is no more than 0.08 mT within 48 h.

This paper presents the results of measurements of fission fragments using a time-of-flight system with a position-sensitive detector based on microchannel plates designed to measure the masses of nuclear reaction products at the MAVR facility. The advantage of such MCPs is their high positional sensitivity and high efficiency of registration of heavy charged particles with low energy. The paper presents a technical description of the fission fragments registration system and the results of measuring the parameters of a position-sensitive detector based on large-area microchannel plates (40 × 60 mm²) obtained by measuring ²⁵²Cf spontaneous fission fragments. The coordinate resolution along the X and Y axes was determined when fission fragments were registered in the ¹⁴N+¹⁹²Au reaction at the MAVR installation. The time resolution of the PSD was obtained by registering the time of flight of alpha particles emitted by the radioactive source ²²⁶Ra.

An experimental setup was created to measure the solubility of substances in supercritical carbon dioxide by a dynamic method, including the possibility of adding a cosolvent to the main solvent: CO₂. A new technique has been developed for determining the mass amount of supercritical carbon dioxide that has passed during the experiment, which is important in determining solubility. Experimental data on the solubility of diphenyl in supercritical carbon dioxide are obtained, which are in good agreement with the literature data, at various state parameters: temperature and pressure. The experimental setup will make it possible to obtain new experimental data in the future on the solubility of a wide range of substances in supercritical carbon dioxide as well as in supercritical carbon dioxide with various organic cosolvents.

A stand is described that is designed to study the emission properties of laser plasma in the extreme ultraviolet range (EUV) formed on liquid jet targets. To form a jet target, a pulse valve and capillaries of various diameters are used. A Nd:YAG laser is used (with a wavelength of 1064 nm, a pulse duration of 11 ns, a frequency of up to 10 Hz, and a pulse energy of 500 mJ) to excite laser plasma. To investigate the emission spectra, a mirror X-ray spectrometer calibrated in absolute units, an Aurora 4000 visible-range spectrometer, and a microscope operating in the EUV range are used. Photographing of the formed liquid jets is also provided. The design of the stand and its main parameters are presented. The results of the first experiments to study the processes of liquid outflow from various nozzles into vacuum are also presented.

The polarization properties of a two-channel spatial AO filter based on diffraction into two symmetric Bragg orders have been studied. A regime is demonstrated where during Fourier processing of an image, the contours in different channels are formed in different polarizations and at different acoustic frequencies. This regime was confirmed experimentally on the basis of optical Fourier processing of an image transmitted by radiation with an optical wavelength of 0.63 μm. As a spatial frequency filter, an AO cell manufactured of paratellurite was used. This made it possible to form the image contour in one channel at a sound frequency of 34 MHz and in another channel at a frequency of 42 MHz.

The article presents the results of the development of a universal radiometric device for measuring the activities of alpha, beta, and gamma radiation and the volumetric activity of radon in soil, air, and water. The structure of a multichannel radiometric device with software, a diagram of a microcontroller unit with a signal conditioner, and the operation of electronic units are presented. The data of monitoring the volumetric activity of radon alpha particles and the activities of beta and gamma radiation in the soil air are given. The monitoring results showed that activities vary depending on temperature, humidity, and time of day. The device is compact, mobile, and universal and can be used both stationary and in the field. The developed RMI V1.7 program allows for long-term, real-time monitoring, and all measurements are displayed on a computer monitor.