Experiments on Sonoluminescence: Possible Nuclear and QED Aspects and Optical Applications

Experiments aimed at testing some hypothesis about the nature of Single Bubble Sonoluminescence are discussed. A possibility to search for micro-traces of thermonuclear neutrons is analyzed, with the aid of original low-background neutron counter operating under conditions of the deep shielding from Cosmic and other sources of background. Besides, some signatures of QED-contribution to the light emission in SBSL are under the consideration, as well as new approaches to probe a temperature inside the bubble. An applied-physics portion of the program is presented also, in which an attention is being paid to single- and a few-pulse light sources on the basis of SBSL.Comment: 4 pages; to be published by AIP in the Proc. ISNA-1

Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity

An optical response of one-dimensional string made of dipoles with a periodically varying density excited by a spot of light moving along the string at the superluminal (sub-luminal) velocity is theoretically studied. The Cherenkov radiation in such system is rather unusual, possessing both transient and resonant character. We show that under certain conditions, in addition to the resonant Cherenkov peak another Doppler-like frequency appears in the radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as different string topologies are considered.Comment: accepted to Phys. Rev.

Modeling the burnout of solid polydisperse fuel under the conditions of external heat transfer

A self-similar burnout mode of solid polydisperse fuel is considered taking into consideration heat transfer between fuel particles, gases, and combustion chamber walls. A polydisperse composition of fuel is taken into account by introducing particle distribution functions by radiuses obtained for the kinetic and diffusion combustion modes. Equations for calculating the temperatures of particles and gases are presented, which are written for particles average with respect to their distribution functions by radiuses taking into account the fuel burnout ratio. The proposed equations take into consideration the influence of fuel composition, air excess factor, and gas recirculation ratio. Calculated graphs depicting the variation of particle and gas temperatures, and the fuel burnout ratio are presented for an anthracite-fired boiler. © 2013 Pleiades Publishing, Inc

Positron annihilation spectroscopy of vacancy-type defects hierarchy in submicrocrystalline nickel during annealing

Positron annihilation and X-ray diffraction analysis have been used to study submicrocrystalline nickel samples prepared by equal channel angular pressing. In the as-prepared samples the positrons are trapped at dislocation-type defects and in vacancy clusters that can include up to 5 vacancies. The study has revealed that the main positron trap centers at the annealing temperature of deltaT= 20°C-180°C are low-angle boundaries enriched by impurities. At deltaT = 180°C-360°C, the trap centers are low-angle boundaries providing the grain growth due to recrystallization in-situ

Optical Properties of Dye-Filled Polymer Films Deposited in Vacuum

The results of investigating properties of polytetrafluoroethylene (PTFE) and polyparaphenylene sulphide (PPS) films filled with dye molecules by co-deposition in vacuum are given. Thin polymer films filled with different polymethine dyes with various dye concentration are investigated. Film properties at room temperature and during heating were studied using optical absorption spectroscopy. It is shown that the polymer matrix prevented dye molecules aggregation, particularly the PTFE matrix prevented aggregation more strongly than the PPS matrix. During heating the PTFE matrix keeps the dye molecules in non-aggregated state up to dye decomposition temperature.Представлено результати дослідження властивостей плівок політетрафторетилену (ПТФЕ) та поліпарафенілен сульфіду (ППС), які були наповнені молекулами барвників за допомогою співосадження у вакуумі. Досліджено тонкі полімерні плівки, що наповнені різними поліметиновими барвниками з різними концентраціями. Властивості плівок при кімнатній температурі і під час нагрівання було вивчено з використанням оптичної абсорбційної спектроскопії. Показано, що полімерна матриця запобігає агрегації молекул барвника, зокрема ПТФЕ-матриця запобігає агрегації сильніше ніж ППС-матриця. Протягом нагрівання ПТФЕ-матриця утримує молекули барвника в не агрегованому стані до температури розкладання барвника.Представлены результаты исследования свойств пленок политетрафторэтилена (ПТФЕ) и полипарафенилен сульфида (ППС), которые были наполнены молекулами красителя с помощью соосаждения в вакууме. Исследованы тонкие полимерные пленки, наполненные разными полиметиновыми красителями с различными концентрациями. Свойства пленок при комнатной температуре и при нагревании были изучены с использованием оптической абсорбционной спектроскопии. Показано, что полимерная матрица предотвращала агрегацию молекул красителя, в частности ПТФЕ-матрица предотвращала агрегацию молекул более сильно, чем ППС-матрица. Во время нагревания ПТФЕ-матрица удерживала молекулы красителя в не агрегированном состоянии до температуры разложения красителя

Evaluation of the structural-phase characteristics of a supersaturated ultrafine-grained Au-Co solid solution by diffractometry in hard synchrotron radiation

A synchrotron radiation study of immiscible Au-Co alloys obtained by consolidating a heterogeneous mixture of components and subsequent severe plastic deformation was performed. Namely, the estimates of the crystal lattice parameter, the average size of the coherent scattering regions and lattice strains in mechanically alloyed supersaturated solid solutions were made using obtained diffraction patterns and diffraction spectra. The effect of the temperature regime of deformation processing on the listed characteristics is shown, when the transition from cold deformation to cryogenic is carried out. © 2020 American Institute of Physics Inc. All rights reserved.The work was done at the shared research center SSTRC on the basis of the VEPP-4 - VEPP-2000 complex at BINP SB RAS, using equipment supported by project RFMEFI62119X0022. The SR XRD performed at the station "Diffractometry in the "hard" X-ray range" of the 4th synchrotron radiation channel of the VEPP-3 accelerator of the Siberian Center of Synchrotron and Terahertz Radiation of the Budker Institute of Nuclear Physics by Alexey I. Ancharov. Obtaining and deformation processing of the investigated materials were carried out on the basis of M.N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg. The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme “Рressure” No. АААА-А18-118020190104-3), supported in part by RFBR (project No. 19-32-60039)

Short-Living Defects and Recombination Processes in Li 6Gd(BO3)3 Crystals

Results of a study of transient optical absorption (TOA) and luminescence of lithium-gadolinium orthoborate Li6Gd(BO3)3 (LGBO) in the visible and ultraviolet spectral regions are presented. As revealed by absorption optical spectroscopy with nanosecond time resolution, the LGBO TOA derives from optical transitions in hole centers, with the optical density relaxation kinetics being mediated by interdefect tunneling recombination involving these centers and neutral lithium atoms acting as electronic Li0 centers. At 290 K, the Li0 centers are involved in thermally stimulated migration, which is not accompanied by carrier transfer to the conduction or valence band. The slow TOA decay kinetics components, with characteristic times ranging from a few milliseconds to seconds, have been assigned to diffusion-limited annihilation of lithium interstitials with vacancies. The mechanisms responsible for the creation and relaxation of short-living Frenkel defect pairs in the LGBO cation sublattice have been analyzed. © 2009 Elsevier Ltd. All rights reserved