Открытый доступ
Доступ предоставлен
Только для подписчиков
Том 60, № 10 (2018)
- Год: 2018
- Статей: 7
- URL: https://journal-vniispk.ru/0033-8443/issue/view/15164
Article
Equidistant Recording of the Spectral Components in Ultra-Wideband Spectral-Domain Optical Coherence Tomography
Аннотация
We develop an effective method for reducing nonequidistance when recording the spectral components of an interference signal in ultra-wideband spectral-domain optical coherence tomography. For this purpose, a corrector consisting of two identical prisms is used in a diffraction-grating spectrometer. The corrector rotation with respect to the diffraction-grating plane and a variation in the angle between the corrector elements allow one to adjust the equidistant spatial distribution of the spectral components in the photoreceiver array. It is shown experimentally that the developed method substitutes digital correction and leads to a significant reduction of the computational load in the optical coherence tomography device.
769-778
On the Possibility of Creating a Point-Like Neutron Source
Аннотация
We consider the possibility of creating a compact high-power neutron generator with a small emitting area (of the order of 100 μm) and a neutron yield of 1010s−1 on the basis of a deuterium–deuterium fusion reaction (or 1012 s−1 on the basis of a deuterium–tritium fusion reaction). The fusion takes place under bombardment of a deuterium- (or tritium-) saturated target by a high-current (about 100 mA) focused deuterium ion beam with an energy of ~ 100 keV. The ion beam with total current at a level of hundreds of milliamperes and small emittance (less than 0.1 π·mm·mrad), which is crucial for sharp focusing, can be generated by a quasi-gas-dynamic ion source of a new generation created on the basis of a discharge in an open magnetic trap sustained by high-power electromagnetic radiation of the millimeter wavelength range under electron cyclotron resonance conditions. Simulations of the focusing system for the experimentally obtained ion beam show the possibility to create a deuterium ion beam with a transverse size of 200 μm on the neutron-forming target. Prospects for using such a neutron source for neutron tomography are discussed.
779-785
Electrodynamic Analysis of Electromagnetic Hybrid Waves in a Ridged Waveguide
Аннотация
We consider an algorithm of calculating the characteristics of the fields of hybrid modes in waveguides with complicated cross sections. The presented algorithm makes it possible to allow for the specific features of the behavior of the electromagnetic-field components near the dielectric and metal ribs of the waveguide. The results of calculating the electrodynamic characteristics of the hybrid HE and EH modes in a Π-shaped waveguide with layered and piecewise-layered dielectric filling are reported. The tables of cutoff wave numbers are presented, and the structures of electromagnetic fields of hybrid modes are shown. The results obtained by using the method proposed and the numerical methods are compared.
786-796
Effective High-Frequency Permeability of Compacted Metal Powders
Аннотация
We propose a model for determination of the effective complex permeability of compacted metal-powder media. It is based on the equality of the magnetic moment in a given volume of the media with the desired effective permeability to the total magnetic moment of metal particles in the external high-frequency magnetic field, which arises due to excitation of electric eddy currents in the particles. Calculations within the framework of the proposed model allow us to refine the values of the real and imaginary components of the permeability of metal powder compacts in the microwave band. The conditions of applicability of the proposed model are formulated, and their fulfillment is verified for metal powder compacts in the microwave and millimeter wavelength bands.
797-807
Collisional Coupling of the Molecular Oxygen 16O2 Fine-Structure Lines Under Low Pressures
Аннотация
We consider collisional coupling between the fine-structure lines of molecular oxygen near 60 GHz under pressures of up to 20 Torr. The observation possibility of the coupling effect manifestation in the oxygen line profile is analyzed by means of numerical simulation. The signal-to-noise ratio required for direct observation of the collisional coupling and deviations of the line parameters from the tabulated values related to the indirect effect manifestation in the spectra are numerically evaluated. By the example of the overlapping profiles of the 13+ and 3− lines, the impact of collisional coupling on the doublet profile is experimentally demonstrated. The results of the analysis of experimental spectra are in good agreement with the results of numerical simulation.
808-823
Coherent Seismoacoustic Sounding of a Model of the Layered Sea Bottom Under Laboratory Conditions
Аннотация
The algorithms developed for reconstructing the geoacoustic parameters of the bottom layers during their coherent sounding are experimentally verified under laboratory conditions. The algorithms use the parametric models of forming the signals reflected from the layered half-space. To solve the problem, an experimental setup for measuring the parameters of the sounding acoustic pulses reflected from a set of elastic layers placed in a water tank is developed at the Acoustics Division of N. I. Lobachevsky State University of Nizhny Novgorod. The devices for forming, radiating, and receiving the acoustic pulses reflected from the layered system are developed. The structure of reverberation interference in the measuring tank is studied. The parameters of the layered-bottom model are experimentally estimated for the optimized parameters of the sounding signals.
824-835
Determination of the Wave Parameters from the Statistical Characteristics of the Image of a Linear Test Object
Аннотация
We statistically analyze the images of the objects of the “light-line” and “half-plane” types which are observed through a randomly irregular air-water interface. The expressions for the correlation function of fluctuations of the image of an object given in the form of a luminous half-plane are found. The possibility of determining the spatial and temporal correlation functions of the slopes of a rough water surface from these relationships is shown.
The problem of the probability of intersection of a small arbitrarily oriented line segment by the contour image of a luminous straight line is solved. Using the results of solving this problem, we show the possibility of determining the values of the curvature variances of a rough water surface.
A practical method for obtaining an image of a rectilinear luminous object in the light rays reflected from the rough surface is proposed. It is theoretically shown that such an object can be synthesized by temporal accumulation of the image of a point source of light rapidly moving in the horizontal plane with respect to the water surface.
836-848