Papers by Keyword: Track Structure

Abstract: Here we discuss the e⁺ fate from its injection into a liquid till its annihilation, namely: 1) energy losses and track structure of fast positrons. Parameters of the terminal e⁺ blob; 2) electric interaction between blob constituents; 3) picosecond stage: hot (epithermal), quasi-free (dry), solvated (hydrated) e^- and e⁺, capture of hot particles by a scavenger; 4) positronium formation in condensed matter: the Ore model, the diffusion-recombination model, formation of quasi-free Ps and Ps in a bubble, a “non-point” positronium; 5) application of an external magnetic field, mixing of ortho- and para-Ps states, R(H)-parameter, Ps contactdensity; 6) diffusion-controlled reactions involving Ps (oxidation and ortho-para conversion) at nanosecond stage, temperature dependence of the reaction rate constants.

Abstract: Radial electron densities within 63-67 μm long ion damage trails, latent ion tracks, created in {001} muscovite by irradiation with 11.1-28.7 MeV/A U and Pb ions, have been derived by small-angle X-ray scattering. Track diameters are 8.0-10.2 nm. The tracks exhibit continuous and uniform electron density decrease of ~4%. Complementary microscopy has revealed loss of atomic order in the tracks. These ion-induced effects undoubtedly accelerate preferential through track permeability of inert and corrosive agents, a property that is important for track applications.

Abstract: Positron annihilation lifetime (PAL) spectra are measured in liquid water in the temperature range 2 – 930C. The spectra are treated by taking into account intratrack reactions and assuming that radical reactions with Ps are diffusion-controlled (the respective temperature dependences obeying the Stokes-Einstein law). Equilibrium Ps bubble parameters are obtained.

Abstract: Certain analytical elastic solution for curvilinear track section under uniform thermal loading has been proposed. Track section is composed of circular arc, transition curves and straight lines. Next step is the analysis of two-dimensional model of the track structure (stress plane, without vertical direction). The rails and the sleepers are assumed as elastic bodies. The fasteners and ballast are modeled as elastic-plastic elements. Non-linear properties of these elements are determined by comparison of numerical data with experimental results. Cyclic uniform thermal field is applied as the load of the system. Pre-buckling analysis is the basic part of the considerations. Certain remarks on the track stability, based on the previous author analyses, are also presented. It is shown that track structure with Y-shaped steel sleepers gives the possibility to use of continuous welded rail (CWR) track practically in any radius of curvature.