Instruments and Experimental Techniques最新文献

A detector of pulsed neutron radiation of the activation type with continuous recording of registered pulses of secondary electrons in real time is described. As activation material, 0.3-mm-thick silver foil is used. An industrial grade SBM-19 gas-discharge Geiger–Muller counter, sensitive to hard beta and gamma radiation, was used to register secondary electrons. The recording interval of the accumulated number of registered secondary electron pulses is 10 s. The circular memory buffer used to record the secondary electron pulses is 16 MB, providing continuous recording for 2.5 years. A modern LiSOCl₂ galvanic cell with a voltage of 3.6 V and a capacity of 2.1 A h was used as a power source for the pulsed neutron radiation detector. The estimated operating time without replacing the battery is 5 years.

This work describes and verifies a method for measuring the intensity in the cross-section of a molecular beam. A scheme has been proposed to take into account the background gas’s influence and was tested. Measurements in argon and nitrogen flow demonstrated a direct dependence on the shape, width, and average size of the transverse profile of the molecular beams under conditions of supersonic jet condensation on the Mach number at the entrance to the skimmer.

This work is devoted to the 3D-design of an all-metal waveguide CO₂ laser (elements and the entire device), the design of which is based on the use of domestic precision aluminum sections. 3D views of the individual units and the entire laser are shown. The schemes of air and water cooling, the technology of assembling and sealing the CO₂ laser using laser (plasma) welding and adhesive joints, which ensure high quality and reliability of the device, are described.

An inspection probe is the key component of a scanning ferromagnetic resonance spectrometer, which is used to measure spectra of electromagnetic radiation absorption in local areas of thin magnetic films. The degree of locality is determined by the area of the measuring aperture in a probe (0.1–2.2 mm²). The spectrometer sensitivity has been significantly increased by miniaturizing the oscillating circuit with a high intrinsic quality factor of the autodyne oscillator and by replacing the round measuring aperture of the probe head with a square one. The square shape of the measuring aperture increases the homogeneity of the high-frequency magnetic field distribution in it. A set of replaceable probes with a required pitch has been designed to cover the frequency range of 0.1–4.0 GHz. The signal-to-noise ratio of a probe with an aperture area 1.0 mm², measured on a permalloy film with a thickness of 2 nm is 8 dB or more. It is shown that the effective saturation magnetization monotonically reaches the saturation M_S = 843 G with frequency rise and abnormally increases by a factor of ~1.6, to M_S = 1359 G at low frequencies. The applicability of the developed probes to study the nature of formation and the peculiarities of the magnetic-inhomogeneity distribution over a sample area is demonstrated by using 25-nm-thick permalloy films (dimensions, 10 × 10 mm²) deposited in a dc magnetic field on monocrystalline langasite substrates.

The results of studies on the generation of a radially converging electron beam in a source with a multiarc grid plasma emitter are presented. Generation modes have been achieved that are sufficient for modifying the surface of metallic materials and cylindrical products with a calculated energy density of up to 20 J/cm² at a pulse duration of up to 500 μs. Using an automated system for measuring plasma parameters and a single Langmuir probe in the range of arc discharge current 50–120 A and pulse duration 50–500 μs, measurements of the distribution of emission plasma parameters in a grid plasma emitter in the azimuthal and axial directions were carried out. Comparisons of the electronic branches of the probe characteristic at different working gas pressures are presented. The created electron source opens up new opportunities for comprehensive modification of the surface of various materials and products of cylindrical or more complex shapes in order to change the functional and operational properties of this surface.

A description of the experimental setup and examples of its application to studying the gravitational settling dynamics of a cloud of bidispersed drops with specified values of their diameters and initial concentration are presented. The main element of the setup is the original device for obtaining a cluster of drops. It is shown that, under the conditions of the performed experiments that are characterized by the formation of a bidispersed cloud upon simultaneous separation of two horizontal layers of monodispersed drops, the cloud moves at the initial settling stage as a single unit. At a certain distance dependent on the drop size, the bidispersed cloud stratifies into two clusters of monodispersed drops, each of which moves in the “blown” cloud mode.

We developed a simple and versatile non-destructive testing method to simultaneously measure the phase velocity and attenuation of ultrasound wave propagation through solid medium. In this technique, a continuous ultrasound excitation emitting from the high-quality lithium niobate transducer passes through the solid medium and the transmitted signal is received by another identical LiNbO₃ crystal. To check the reliability of this method, the velocity and attenuation of both longitudinal and shear ultrasound waves have been measured at room temperature in aluminium and copper correspondingly which are consistent with previous research. Moreover, the versatility of this technique has been shown from the phase velocity measurement of the longitudinal excitation as a function of temperature which depicts interesting anomalies across the Verwey transition in Fe₃O₄ and critical temperature of ferromagnetic ordering in SrRuO₃, respectively.

The frequency mode of operation (1 pulse/s) of a source of low-energy, high-current electron beams based on an explosive-emission cathode with built-in arc plasma sources initiated by dielectric surface flashover was investigated. It has been shown that the source stably (without missing) generates the beam in the modes of vacuum and gas-filled diode at a prescribed pulse repetition rate and charge voltages of the generator supplying an electron gun of 5–20 kV.

Experimental techniques and methods of experimental data processing for monitoring of controlled neutron fluence with energies greater than 0.1 MeV are described. The approximation of fast neutron fluence values on the basis of experimental values of neutron fluence with energies greater than 1 and 3 MeV, directly measured by Nb- and Fe-monitors, is necessary for the assessment of radiation damage of materials in support of safe operation of nuclear reactors. Reliability of determination of fast neutron fluence values in controlled points of the irradiation device is confirmed by comparative analysis of calculated and experimental data.

Herein is proposed a method for controlled rotation of the plane of polarization of linearly polarized radiation based on the addition of two mutually orthogonal elliptically polarized waves, the parameters of which are controlled by an acoustic wave in the process of acousto-optical (AO) Bragg diffraction. It has been shown theoretically that the angle of polarization rotation depends on the ellipticity of the beams and does not depend on the wavelength of the light. The maximum polarization rotation is determined by the ellipticity of the combined waves and can reach approximately 45°. Experiments on controlling the polarization rotation of optical radiation with a wavelength of 0.63 μm, performed on the basis of an AO cell made of a paratellurite crystal, confirmed the main theoretical conclusions.