Preliminary studies on a variable energy positron annihilation lifetime spectroscopy system

There are many advantages in being able to perform positron annihilation lifetime spectroscopy (PALS) using a variable energy positron beam, the most obvious being the easy identification of different defect types at different depths. The difficulty in conducting variable energy (VE) PALS studies lies in the fact that a “start” signal is required to signal the entry of the positron into the target. Two methods have been used to overcome this problem, namely the bunching technique, which employs radio frequency (RF) cavities and choppers, and secondly the use of secondary electrons emitted from the target. The latter technique is in terms of experimental complexity much simpler, but has in the past suffered from poor time resolution (typically ∼500 ps). In this work, we present a series of computer simulations of a design based on the secondary electron emission from thin C-foils in transmission mode which shows that significant improvements in time resolution can be made with resolutions ∼200 ps being in principle possible.     

Phasing of three vircators simulated in terms of coupled van der Pol oscillators

Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found.     

New Plasmon Waveguides Composed of Twin Metal Wedges with a Nano Gap

We have numerically shown the existence of coupled wedge plasmons (CWPs) which propagates along a nano gap of a twin metal wedge. The CWPs are formed by wedge plasmons which can interact with each other. The dispersion relations of the wavenumber, propagation distance, and beam area of CWPs, are described and show that the characteristics of CWPs are similar to those of wedge plasmons and of gap plasmons. We also propose a new plasmon waveguide composed of twin metal wedges with a nano gap.     

Composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene

The composition and structure of low-molecular-weight products of thermal oxidative degradation of atactic polypropylene were studied.     

Fundamental aspects of initiated oxidation of tridecane and polyethylene in solutions

Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.     

Thermodynamic properties of ternary systems: Calculation of standard enthalpies of solvation of triols, diols, and a series of their ethers in water-methanol mixed solvent

An equation for the standard enthalpy of solvation of a compound in a binary solvent is derived. The enthalpies of solvation in water-methanol mixtures are estimated for 1,3-propane-and 1,6-hexanediols, 1,2,4-butane-and 1,3,5-pentanetriols, 2-methoxy-and 2-propoxyethanols, and diethylene glycol. The enthalpy of solvation of 1,2-dimethoxyethane in the water-methanol mixed solvent is determined experimentally.     

Fractal Structure in Ionization Dynamics

Chaotic dynamics in open systems produces fractals. This can be seen, for example, in the ionization of an electron from a hydrogen atom in applied parallel electric and magnetic fields. We summarize some of our recent work on the order that can be found in these fractals.     

Recovered-voltage phenomenon and prospects for its use for assessment of the condition of polymers

A general theory of the phenomenon of recovered voltage in polymers was considered on the basis of representation of an actual poling process by a discrete set of Debye relaxators. Examples of numerical solution of the direct and inverse problems are given. A correlation expression between intentionally aged polymer specimens and recovered-voltage curves was proposed for use in the assessment of the material state of a polymer under actual service conditions. It was shown that it is sufficient to restrict consideration to three relaxation processes in analysis of the phenomenon.