Instruments and Experimental Techniques最新文献

An improved prototype of the large-aperture, high-resolution spectrometer−polychromator (the so-called high-etendue spectrometer, HES) has been designed for spectroscopy diagnostics of plasma, in particular, for the Charge-eXchange Recombination Spectroscopy (CXRS) diagnostics at the ITER facility. Ion temperature profiles, poloidal and toroidal plasma rotation velocities, and low-Z impurity densities can be measured using the CXRS technique. The HES is equipped with novel, high-efficiency compact sCMOS cameras with low noise level, wide dynamic range, high quantum efficiency, and almost 100% working cycle. The HES is based on three transmission holographic gratings, which allow its simultaneous operation in three spectral bands: 468 ± 5, 529 ± 5, and 656 ± 6 nm. The main performance characteristics of the cameras, transmission gratings, and the spectrometer as a unit have been measured. It has been established that the characteristics of the developed HES satisfy the requirements for the spectroscopic equipment intended for measurements of the ITER CXRS diagnostic system.

An experimental setup for studying pulse gas flows within short periods (up to 1 ms) was developed and an experimental data processing method is presented. Based on high-speed frame interferometry data and the results of dynamic pressure measurements, the spatial and temporal distributions of the helium flow density and velocity are determined. The optimal method for reconstructing the spatial density distributions with consideration for the experimental errors is described. The presented method allows characterization of the gas flows with a density of more than 0.0001 kg/m³ and a velocity of more than 400 m/s.

A sensor of micrometeoroids and space debris particles based on the detection of reflected and scattered laser radiation, when a particle passes through an optical barrier, is described. A design of the primary transducer of the sensor is proposed, a theoretical analysis of its resolution is performed, and its circuit implementation is described. The ray tracing method was used to simulate its operation using specialized software.

An experimental facility has been developed by MEPhI to study the spectrometric characteristics of gas mixtures for cascade gas electron multipliers (GEMs), which are widely used in modern tracking, Cherenkov, and synchrotron-radiation detectors designed for high-energy physics experiments. The characteristics of the gas mixture for the GEMs used in the BM@N international experiment (Joint Institute for Nuclear Research, Dubna) have been investigated. The applicability of this facility for laboratory works accompanying the Nuclear Physics and Technology master’s courses is noted.

One of the methods for obtaining ¹²³I is the bombardment of gaseous ¹²⁴Xe with protons, in which nuclear reactions of production and decay of ¹²³Xe and ¹²³I isotopes occur. After irradiation, the gas phase is condensed from the target into a special “decay container,” in which the target isotope ¹²³I is produced and accumulated during ¹²³Xe decay. The amount of ¹²³I produced in the target and deposited on its walls during the irradiation is comparable to the amount of ¹²³I obtained in the decay container. A laboratory setup has been created and a process technology for extracting ¹²³I from the walls of the target has been developed to increase the total yield of ¹²³I. Organic solvents (acetone and diethyl ether) are used for this purpose. The proportion of the ¹²³I extracted by washing off from the walls of the aluminum target is at least 84%. The loss during subsequent vacuum distillation of solvents does not exceed 5%. After vacuum distillation, the extracted ¹²³I is dissolved in NaOH. At this stage, the efficiency of ¹²³I washing-off with a 0.01 M NaOH solution is at least 95%. Nevertheless, even taking into account these losses, the proposed method makes it possible to additionally extract the ¹²³I radionuclide from the target in an amount equal to or greater than the activity of the ¹²³I produced using the existing technology.

The design of the portable Wilson cloud chamber and devices included in it are described. The main performance characteristics of these devices are presented. Multiple tests of the setup have been carried out, and the main parameters of its functioning, as well as the required parameters of the cooling system, have been determined. This Wilson cloud chamber is used as the scientific, laboratory, and demonstration equipment.

A packaged power detector made in a waveguide with a standard cross section of 2.4 × 1.2 mm² for the three-millimeter wavelength range with good enough matching for this type of device is presented. The design uses low-barrier diodes made on the structure of domestic production. The calculated and experimental characteristics of the detectors are given, such as the frequency dependence of the sensitivity and the level of the standing wave ratio (SWR). It is shown that the average sensitivity of the detectors over the range is more than 1000 V/W, and the SWR value is no more than 3.

A photodetector was prepared by depositing PEDOTPSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] and TPD polymer (p-TPD) [N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine] on porous silicon (PSi) substrates with a spin coating technique. The value of the response time (4.419 s) of the manufactured PS/PEDOT : PSS/TPD detector (by illuminating the sample with a 250 W/cm² tungsten lamp) was measured in second’s scale. The detection was 3.9 × 10⁸ W⁻¹, specificity—2.3 × 10⁸ W⁻¹ Hz^1/2 cm and optical response—8.85 × 10⁻³ A/W. The incorporation of AgO nanoparticles with a TPD polymer improved the detection to 80.06 × 10⁸ W⁻¹, specificity − to 46.4 × 10⁸ W⁻¹ Hz^1/2 cm, optical response—to 2.01 A/W, and detector response time—to 5.3 ms. The measurements taken by Hall show that the n-type nanoparticles have a carrier concentration of ×10¹⁷ cm⁻³.

The design and parameters of a compact excilamp with an original sealed-off emitter made of a quartz tube with an outer diameter of 21 mm are described. The characteristics of xenon radiation in the vacuum ultraviolet region of the spectrum have been studied. On the band of the second xenon continuum, which has a maximum at the wavelength λ ≈ 172 nm, at a pulse repetition rate of 96 kHz, a radiation power density of 30 mW/cm² was obtained. The excilamp was used for excitation of polymethyl methacrylate, in which a photoluminescence band was recorded in the spectral region of 380–480 nm.

A description and characteristics of the developed internal quantum efficiency (IQE) meter for InGaN LEDs are presented. The meter allows one to determine the IQE of LEDs in the current range up to 25 mA by measuring the watt-ampere characteristic and solving a system of equations relating the values of the radiation power of the LED at two currents with an approximating function obtained on the basis of the ABC model (models of recombination of charge carriers in a light-emitting heterostructure, where A, B, and C are the coefficients of nonradiative, radiative, and Auger recombination, respectively). Unlike the well-known Russian and foreign analogues, the IQE meter is characterized by simplicity of hardware implementation and allows determining the IQE of LEDs at room temperature. The operation of the meter was tested on the example of measuring the IQE of commercial green and blue InGaN LEDs. The meter can be used in scientific laboratories as well as in the input control of enterprises–manufacturers of LED products.