PATTERN FORMATION IN CONVECTIVE MEDIA

I.V. Gushchin, А.V. Kirichok, V.M. Kuklin

Full Text :   (4400 kB, Eng.) 

Abstract
The several models of convection in a thin layer of liquid (gas) with poorly heat conducting boundaries are considered. These models demonstrate a rich dynamics of pattern formation and structural phase transitions. The primary analysis of pattern formation in such a system is performed with using of the well-studied Swift-Hohenberg model. The more advanced Proctor- Sivashinsky model is examined in order to study the second-order structural phase transitions both between patterns with translational invariance and between structures with broken translational invariance but keeping a long-range order. The spatial spectrum of arising structures and visual estimation of the number of defects are analyzed. The relation between the density of defects and the spectral characteristics of the structure is found. We also discuss the effect of noise on the formation of structural defects. It is shown that within the framework of the Proctor-Sivashinsky model with additional term, taking into account the inertial effects, the large-scale vortex structures arise as a result of the secondary modulation instability.

KEY WORDS: Rayleigh-Benard convection, mathematical modeling, dissipative structures, structural phase transitions, structural defects

HIGH CURRENT PLASMA ACCELERATORS: PHYSICS AND APPLICATIONS

I.E. Garkusha

Full Text :   (3800 kB, Eng.) 

Abstract
In this review paper, basic principles of high current plasma accelerators, history and recent state of their investigations in IPP NSC KIPT are briefly described. In such devices an internal magnetic field is created by high current up to several MA in the discharge and it is used for both plasma flow acceleration up to 1000 km/s. Particular attention is paid to the quasi-stationary plasma accelerators (QSPA), where discharge duration exceeds considerable the plasma flight time in acceleration channel. Application of QSPA for plasma-surface interaction studies relevant to thermonuclear reactors, like ITER and DEMO, is discussed. Results on surface modification and improvement of material properties by powerful pulsed plasma processing are described. Potential technological applications for materials treatment are emphasized.

KEY WORDS: plasma accelerator, high-energy streams of dense plasma, plasma-surface interaction, surface modification, extreme conditions of thermonuclear reactor ITER

STUDY OF NEUTRINO PROPERTIES AND WEAK INTERACTION IN DOUBLE BETA DECAY EXPERIMENTS

F.A. Danevich

Full Text :   (1150 kB, Eng.) 

Abstract
Investigation of the neutrinoless double beta decay is a unique way to probe physics beyond the Standard Model. The process is sensitive to the lepton number violation, the nature of neutrino (Majorana or Dirac particle), an absolute scale of neutrino mass and the neutrino mass hierarchy. Neutrinoless double beta decay is still not observed, only limits on its half-life were set in the most sensitive experiments. The searches for double beta decay are carried out by different methods, in particular with low-background scintillation and semiconductor detectors. To determine a neutrino mass hierarchy new generation experiment should be sensitive to the effective neutrino mass 0.02 - 0.05 eV, which corresponds to the half-lives T_1/2 ~ 10²⁶ - 10²⁷ years and requires ultra-low background detectors with a high energy resolution applying hundreds kilograms of the isotope of interest. Low temperature scintillating bolometers are the most promising technique for such experiments.

KEY WORDS: double beta decay, neutrino, weak interaction, low counting experiment

PRODUCTION OF CHARMONIUM AND JETS IN ULTRARELATIVISTIC PROTON–PROTON COLLISIONS

A.V. Dieiev, V.V. Kotlyar, N.I. Maslov

Full Text :   (6700 kB, Eng.) 

Abstract
Production of J/ψ-meson in association with jet in proton-proton collisions is studied at energy s^1/2 = 8 TeV. Jet pair production at s^1/2 = 7 TeV is considered briefly. Event generator Pythia 8 is employed in the simulations of the reactions. Distributions that depend on differences of transverse momenta, rapidities y_mj, and azimuthal angles φ_mj of the meson and jet are calculated. It is analyzed, how gluon radiation in initial and final states of the partonic processes along with multiple parton interactions influence the observables. Shapes of (y_mj, φ_mj, y_J/ψ)- and (y_mj, p_{T J/ψ}, y_J/ψ)-distributions, with p_{T J/ψ} (y_J/ψ) being momentum (rapidity) of J/ψ, are shown to differ substantially for the mesons, emitted in the central and forward regions. The observables, measurements of which will help to impose severe constraints on used models, are discussed.

KEY WORDS: event generator Pythia, charmonium, jet production, proton-proton collisions, the LHC, experiments ALICE, ATLAS, CMS, LHCb

HIGH-ENERGY WAVE PACKETS. ‘HALF-BARE’ ELECTRON

N.F. Shul’ga, S.V. Trofymenko

Full Text :   (2200 kB, Eng.) 

Abstract
The evolution in space and time of localized high-energy electromagnetic wave packets, which take place in processes of radiation by ultra relativistic electrons is considered. It is shown that high energies make stabilizing influence on the motion of such packets and that the lengths, within which their dispersion and reconstruction into the packets of diverging waves occurs, can be macroscopic. The electromagnetic field evolution in the process of ultra relativistic electron emission from substance into vacuum is considered. It is demonstrated, that in this case the electron can be in 'half-bare' state with considerably suppressed low frequency Fourier-components of the field around it during long period of time after the emission. It is shown that such state of electron can manifest itself in significant dependence of further ionization energy losses of the electron in thin plate situated in the direction of the particle motion on the distance between the plate and the scattering point.

KEY WORDS: electromagnetic wave packets, ionization energy losses, transition radiation, density effect, 'half-bare' electron

STRANGE QUARK MATTER IN A STRONG MAGNETIC FIELD

А.A. Isayev

Full Text :   (1300 kB, Eng.) 

Abstract
Thermodynamic properties of strange quark matter are considered in strong magnetic fields up to 10²⁰ G. It is shown that the appearance of the longitudinal (along the magnetic field) instability beyond some critical magnetic field precludes the formation of fully polarized quark states in strange quark matter as well as prevents a significant drop of strangeness which, otherwise, could happen in such ultrastrong magnetic fields

KEY WORDS: strange quark matter, strong magnetic field, pressure anisotropy, longitudinal instability

BEAM DYNAMICS IN OUTPUT CHANNELS FROM RECIRCULATOR SALO

I.S. Guk, S.G. Kononenko, F.A. Peev, A.S. Tarasenko

Full Text :   (8600 kB, Eng.) 

Abstract
Optimization of recirculator SALO magnetic structure allowed to refine essentially parameters of electron beams in input points of output channels in the basic observational halls. Parameters of a beam along a trajectory of a motion and on an exit of the basic channels are given. Calculations are spent taking into account non-linear fields of dipole and quadrupole recirculator magnets.

KEY WORDS: electron, recirculator, dipole magnet, quadrupole lens, SALO.