System of pulsed solar energy supply of ionizing radiation detectors

The development of power supplies for ionizing radiation detectors is a complex and difficult problem, especially if this concerns with autonomous mobile measuring systems. In this article, we describe the experience of the implementation of the autonomous solar energy supply for semiconductor ionizing radiation detectors.     

Generation of giant pulses of scattered radiation on the moving front of a pump wave

To generate high-power short-wavelength pulses during the process of the stimulated scattering of a high-power pump wave on a relativistic electron beam, the use of the displacement of a pump spot along the electron flow with the group velocity of the scattered beam has been proposed. Under such conditions, the scattered radiation will be a monopulse with the amplitude increasing proportionally to the displacement of the pump spot due to the energy transfer from unmodulated electron fractions. In the case of an optical laser pump, depending on the direction of the wave vector of the pump field relative to the translational motion of electrons, the new mechanism can be used to generate high-power pulses in terahertz (Doppler down conversion) or ultraviolet (up conversion) bands.     

Dynamics of lasers with two-dimensional distributed feedback

A model of a laser exploiting two-dimensional (2D) distributed feedback is developed. A new feedback mechanism can be realized using a dielectric structure with the width having double-periodical sinusoidal or chessboard modulation. It is shown that 2D Bragg resonator possesses high selectivity over both the longitudinal and the transverse indices. Within semi-classical approach nonlinear dynamics of 2D distributed feedback laser (DFL) is studied and spatial synchronization of radiation from extended active medium is demonstrated.     

Quasi-optical assessment of the ALMA band 9 front-end

The ALMA band 9 (600–720 GHz) receiver is a dual channel heterodyne system which is capable of detecting orthogonally polarised signals utilising a wire grid beam splitter. Two Superconductor–Insulator–Superconductor (SIS) mixers mounted behind hybrid mode corrugated horns are coupled to the 12 m Cassegrain antenna via a wavelength independent configuration of two off-axis elliptical mirrors.We outline an approach involving accurate physical optics simulations in conjunction with precise experimental measurements of the complete optical front-end which guarantees the highest performances. This practical verification approach can be generalised to all quasi-optical receivers to validate system performance. In this paper, we verify the optical design and estimate antenna system efficiency. Comparison between measurement and simulation indicates precise information is achievable in estimating system performance allowing potential improvements in ALMA instrument calibration accuracy.     

Bragg diffraction of light in synthetic opals

Three-dimensional light diffraction from the crystal structure, formed by closely packed a-SiO₂ spheres of submicron size, of samples of synthetic opals was visualized. The diffraction pattern of a monochromatic light beam was established to consist of a series of strong maxima whose number and angular position depend on the wavelength and mutual orientation of the incident beam and the crystallographic planes of the sample. The diffraction patterns were studied under oblique incidence on the (111) growth surface of the sample and with light propagated in the (111) plane in various directions perpendicular to the sample growth axis. The spectral and angular relations of diffracted intensity were studied in considerable detail in both scattering geometries. The experimental data are interpreted in terms of a model according to which the major contribution to the observed patterns is due to Bragg diffraction of light from (111)-type closely packed layers of the face-centered cubic opal lattice. The model takes into account the disorder in the alternation of the (111) layers along the sample growth axis; this disorder gives rise, in particular, to twinning of the fcc opal lattice.     

Structural and optical properties of single and bilayer silver and gold films

Physics of the Solid State - An experimental study of structural and optical properties of silver and gold thin films, as well as bilayer films based on these metals, has been carried out. To study...     

The Influence of a Crystallographically Atypical Pentagonal Nanostructured Coating on the Limiting Stage of Low-Temperature Hydrogen Transport through Pd–Cu Membranes

Doklady Physics - A new approach to the acceleration of the surface processes of hydrogen transport through Pd–40%Cu membranes by depositing a developed catalytic coating consisting of...     

Estimation of the Aggregate Stability of Silver Nanoparticles in a Gel Composition

Russian Physics Journal - The aggregate stability of silver nanoparticles (Ag – NPs) in a gel composition is estimated. It is established that during long-term storage (for 3 years), a...     

Recovery factors for a permeable surface and a gas surface film in a supersonic turbulent boundary layer

The recovery factor on a permeable surface has been experimentally determined at various rates of injection of air into a supersonic turbulent boundary layer. On the basis of an analysis of the solutions of the integral momentum and energy equations for a turbulent boundary layer an expression is obtained for the recovery factor. The recovery factor in the region of a protective gas surface film in a supersonic external flow has been experimentally determined.Moscow. Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp. 131–136, March–April, 1972.