Status of heavy element research using a gas-filled recoil separator at RIKEN

A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element ²⁷¹[110] have been performed using the ²⁰⁸Pb(⁶⁴Ni,1n)²⁷¹[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope ²⁷¹[110] of element 110.     

Color Zone Map in Peripheral Vision at Various Illuminance Levels

We measured the entire region of mesopic and photopic vision to determine the color zone covering the visual field with unique red, yellow, green, and blue hue components. Eight kinds of test stimuli in the natural color system (NCS) color notation system were used. These stimuli were presented at horizontal and vertical meridians, and at meridians inclined at 45° angles. The illuminance level was set at six levels: 0.01 lx-1000 lx. The evaluation method measured chromatic, white, and black components as well as the hue component of the stimuli. Results show that the color zone of the retina extended further into the periphery with increasing illuminance; the response of opponent colors y-b was shown to be greater than that of the opponent colors r-g.     

Real-time color holographic interferometry devoted to 2D unsteady wake flows

A new optical technique based on real time holographic interferometry in true colors has been implemented around the transonic wind tunnel of the ONERA-Lille center to analyze 2D unsteady wake flows. Tests realized in color interferometry, real time and double exposure, use simultaneously three wavelengths of a continuous waves laser (argon and krypton mixed) and holograms are recorded on silver-halide single-layer panchromatic Slavich PFG03c plates. The very principle of real-time true color holographic interferometry uses three primary wavelengths (red, green and blue) to record, under no-flow conditions, the interference among the three measurement beams and the three reference beams simultaneously on a single reference hologram. After the holographic plate is developed, it is placed on the test setup again in the position it occupied during exposure and the hologram is illuminated again by the three reference beams and three measurement beams. A flat, uniform color can then be observed behind the hologram. So a horizontal, vertical, or even circular fringe pattern can be formed and the achromatic central fringe can be made out very clearly. The single color is used to determine the path difference zero on the interferograms. The flow studied was the unsteady flow downstream of a cylinder placed crosswise in the test section. A sequence of hundred interferograms was recorded on the flow around the cylinder at Mach 0.37. The vortex formation and dissipation phases can be seen very clearly, along with the fringe beat to either side of the cylinder.     

Kinetic interpretation of the structural-time criterion for fracture

The incubation-period-based criterion for fracture is considered in terms of the Zhurkov kinetic model of fracture. Within the kinetic model, fracture is treated as a continuously developing process, which starts immediately after the application of a tensile load to a sample and consists in breaking of the interatomic bonds and gradual accumulation of broken bonds in the material in the course of a fracture test. For certain materials, the inclusion of the thermal-fluctuation mechanism for fracture in the incubation-period-based criterion significantly affects the position of the static branch of the time dependence of strength. Time dependences of strength are calculated for a number of materials. The experimental data are analyzed using the structural-time criterion for fracture, which allows one to obtain a unified time dependence of strength for quasi-static and high-rate short-term loadings. The temperature dependence of the incubation period (latent time) is calculated analytically, and a relation is found between the latent fracture time and the thermal vibration frequency of atoms.     

Use of ultrafine-dispersed nanodiamond for selective deposition of boron-doped diamond films

A suspension of ultrafine-dispersed nanodiamond was used for introducing (in particular, selectively) high-density centers of diamond nucleation on various substrates. High-quality doped diamond films to be used as electrochemistry electrodes were deposited from the gas phase in a microwave discharge on certain substrates treated using ultrafine-dispersed nanodiamond. A uniform distribution of nucleation centers with concentrations greater than 10¹⁰ cm^-2 on silicon substrates was obtained. Electrochemical current-potential curves were measured for continuous films. Diamond meshes of different transparency were grown using selective nucleation. Successful production of high-quality doped diamond meshes gives grounds to consider them the most promising electrodes for use in electrochemistry.     

Chain decay of low-angle tilt boundaries in nanocrystalline materials

In terms of two-dimensional dislocation-disclination dynamics, a theoretical model is developed to describe the decay of a low-angle tilt boundary in a deformed nanocrystalline material under the action of an externally applied elastic stress and of the elastic field of a neighboring decayed boundary. The critical external stresses are calculated at which the boundary decays and the dislocations making up this boundary either are trapped by the boundary that decayed earlier or break away from both boundaries. The decay of a low-angle tilt boundary is shown to result in a substantial decrease in the critical decay stresses for the neighboring boundaries, which can cause an avalanche-like chain decay of low-angle boundaries yielding high-density ensembles of mobile dislocations capable of carrying substantial plastic deformations and of forming shear bands in deformed nanocrystalline materials.     

Numerical simulation of the translational nonequilibrium zone behind a shock-wave front

The translational nonequilibrium zone in a shock wave is considered for a gas consisting of light particles and a small addition of heavy particles. The gas is taken to be two-dimensional, and long-range forces are assumed to be absent. In the framework of this approximation, a program for molecular dynamics simulation of the gas is developed. It is applied to calculate a particle distribution function in the shock wave, to analyze the time evolution of the distribution function, and to study its dependence on the gas composition.     

Effect of γ radiation from <Superscript>60</Superscript>Co on the formation of metal contacts to GaAs (Al<Subscript>x</Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>As) structures

The properties of nonrectifying AuGe/GaAs (Al_0.4Ga_0.6As) contacts exposed to heat treatment, ⁶⁰Co γ radiation, and γ radiation combined with the application of an electrical bias are studied. A correlation between the type of interfacial interaction in the contacts and their resistance is found. Results obtained are explained in terms of a diffusion model with a movable boundary of the metal layer.     

Structure and properties of TiC-TiNi composites alloyed with iron

The structure, composition, and mechanical properties of iron-alloyed TiC-TiNi composite materials are studied. When the titanium carbide framework is sintered with iron and then impregnated with titanium nickelide, iron atoms are found to diffuse into the matrix and form the B2 structure that is inhomogeneous (gradient) in chemical composition and properties and exhibits various temperatures of martensitic transformation. The latter fact shows up in the broadening of the martensitic transformation hysteresis and its shift toward low temperatures with increasing iron content. At room temperature, the strength properties of gradient-matrix TiC-TiNi composites are shown to increase with iron concentration.     

Stimulated raman scattering in fiber-optic communication lines

Stimulated Raman scattering (SRS) in a long-distance fiber-optic communication line with wavelength-division multiplexing (WDM) is studied theoretically at a high power of the signal transmitted. A new criterion for determining the SRS threshold is used to calculate the critical input power versus the number of optical channels and frequency separation between them. The theoretical model is verified experimentally. SRS interaction between two channels in a communication line with an SRS amplifier for which the optical waveguide of the line serves as a nonlinear medium is measured.