High-Power Free-Electron Masers Based on Linear Induction Accelerators

Radiophysics and Quantum Electronics - We review the results of theoretical and experimental studies of high-power free-electron masers (FEMs), which are performed jointly by the Joint Institute...     

Applications of x-ray investigations of polymers under load. 1. Measurements of WAXS reflections shifts induced by elastic stretching of oriented polymer systems along their orientation axis

What information can be obtained by wide-angle x-ray scattering (WAXS) from elastic deformation of oriented polymer systems along their orientation axis? This article is a critical review and some generalization of answers for this question. Different cases are analyzed that occur in practice or that might occur in the future: (1) determination of Young's moduli E _c of crystalline lattices parallel to the polymer chains and establishment of correlations between E _c and chain conformation in crystalline lattices; (2) estimation of elastic properties of different fragments of polymer chains, especially of multiatomic complex fragments; (3) detection of conformational polymorphism in crystalline lattices; (4) determination of Poisson's coefficients of crystalline lattices; (5) estimation of potential ability of a given polymer for formation of systems with high moduli; (6) estimation of structural inhomogeneity of amorphous polymers; (7) study of interaction character of structural elements in oriented polymer blends; (8) investigations of systems with a combination of extended and folded-chain crystals; (9) study of influence of cross-linking on structure-mechanical behavior; (10) estimation of adhesive interaction of different components in polymer composites. Only Points 1 (see, e.g., Refs. 1–18) and 4 [19] have been considered in earlier literature by other authors, mainly for soft-chain polymers. Thus, similar results are considered here only briefly, and primary attention is focused on the peculiarities of investigations of rigid-chain polymers. As for the other points, they were considered earlier in our separate works [20–38] (or have not been considered at all) and up to now have not received wide acceptance. During the consideration here, both series and parallel models of interactions of different structural elements were used.     

Measuring of mass and spin of dark matter particles at ILC

In many models stability of dark matter particles D (with mass M _D ) is ensured by a new conserved quantum number which we call the D-parity. We consider models which also contain charged D-odd particle D ^± (with mass M _±). We study the process e ⁺ e ^? ?? D ⁺ D ^? followed by decay of D ^± to D and gauge bosons W (either on-shell or off-shell). Measuring the end points of the energy distribution of W??s would determine M _D and M ^±. However, the hadron mode of W decay would lead to low precision in this measurement. while the information from the lepton mode looks incomplete. I show that it is sufficient to measure the energy distribution of a single lepton (for definiteness ??) in the process e ⁺ e ^? ?? ?? + 2jets + large missing E _T . The well identified singularities in this distribution allow for determination of M _D and M _± with a high precision. After that, measuring the corresponding cross section will allow one to determine the spin of D particles.     

Effect of fullerene C<Subscript>60</Subscript> on the structure and mechanical characteristics of polyethylene: Technological aspect

On the basis of the literature data, a retrospective analysis of the thermodynamic characteristics of dissolution of fullerene C₆₀ in a series of single-ring aromatic solvents is presented. The effect of the molecular structure of a solvent on its dissolving capacity with respect to fullerene is studied. The parameter of the boiling temperature of the solvent normalized to its molecular mass is introduced. The correlation of this parameter with the dissolving capacity of the solvent is discussed. Special emphasis is placed on the effect of halogen-containing solvents on the dissolution of fullerene and indirectly on the development of the mechanical characteristics of films prepared from common solutions of fullerene and low-density polyethylene. For comparison, the films prepared from PE melts modified with low concentrations of fullerene are considered. The film structure is studied via X-ray analysis, optical microscopy, AFM, small-angle scattering of linearly polarized light, and DSC. The films with the maximum strength are prepared from solutions in halogen-containing solvents at a concentration of fullerene below 1 wt %. In this case, spherulites are 5–10 times smaller than those in the films cast from solutions in other solvents. In the films cast from common solutions of PE and fullerene in bromobenzene, crystal solvates C₆₀ · 2C₆H₅Br are formed. It seems that the formation of the crystal solvates binds the residual solvent and thus affects the mechanical behavior of the films, thereby eliminating the plasticizing effect of residual bromobenzene. Localization of fullerene in various regions of the supramolecular structure of the films is discussed, and the morphology of the separating regions of the crystal solvate fullerene phase is analyzed.     

Effect of fullerene black additions on the tribological properties of armamid PA SV30-1

The tribological properties of Armamid PA SV30-1 material with additions of fullerene black were studied using LZ-TsNII(U) plastic lubricant.     

Collective spontaneous emission in a distributed feedback laser with an inhomogeneously broadened active medium

Peculiarities of the implementation of a superradiant generation mode in a laser with a distributed feedback of the waves and an inhomogeneously broadened spectral line of the active medium are investigated. Based on a numerical solution of the semiclassical Maxwell-Bloch equations for the amplitudes of counterpropagating electromagnetic waves, polarization, and inversion of a two-level medium population, it is shown that a sequence of coherent high-power pulses is generated by the Bragg structure in a wide range of the laser parameters as a result of the selected mode and the cw pumping.     

Powerful Cherenkov oscillators with 2D distributed feedback

The feasibility of using 2D distributed feedback based on 2D planar and coaxial Bragg structures for generating spatially coherent radiation from rectilinear ribbon and tubular electron beams is studied. One-section and sectional Cherenkov masers are analyzed. In the former design, a 2D Bragg structure acts as a resonator and a periodic slow-wave system simultaneously. In the latter (sectional) design, radiation is synchronized in a 2D Bragg structure that is placed at the cathode end of the interaction space and couples longitudinal and transverse (azimuthal) wave flows. The wave is amplified by the electron beam mainly in the fairly long middle section. The output (collector) part contains a standard 1D Bragg structure that partially reflects the amplified radiation toward the cathode and closes the feedback circuit. It is shown that dissipation introduced into the 2D Bragg structure of the sectional design makes it possible to increase one of the transverse sizes of the system to ∼10³ wavelengths with the energy exchange efficiency and one-frequency masing mode stability remaining the same. With such an overdimension, the millimeter-wave radiation integral power may reach a gigawatt level.