Neutron emission during a nanosecond discharge in deuterium in a nonuniform electric field

Neutron emission during a nanosecond deuterium discharge formed at the nonuniform electric field is investigated. A stable neutron yield is observed when the cathode is made of metallic plates covered by a layer of deuterated zirconium and the anode is made of stainless steel in the form of a tube. It is shown that, when the deuterium pressure equals several Torr, neutrons are emitted from both deuterated and deuterium-free cathodes. The influence of the anode design on the neutron yield is studied.     

Formation of relief on a metallic target surface under the action of compression-plasma flows

The results of experimental and theoretical investigations of relief formation on the surface of a steel target (grade St 3 steel, GOST (State Standard) 380) during treatment by compression-plasma flows are represented. The density of energy absorbed by the target varied in the range from 15 to 25 J/cm², the pulse duration was 100 μs, and the pulse number was N = 1, 3, 5, 7. The experiment revealed the expansion of boundaries of the central area (the area on which the plasma flow is incident normally to the surface) with increasing pulse number. This is explained by the more uniform surface treatment at a greater pulse number. It is shown that to describe relief formation in the central area there is a need to take into account the pressure of the plasma flow on the target surface, apart from surface tension forces and energy dissipation due to viscosity.     

Production of sapphire tubes for high-pressure sodium lamps using the stepanov method at high rates of growth

The process of the Stepanov growth of sapphire tubes is studied at the growth rates up to 20 mm · min⁻¹ in a Mo crucible with graphite succeptor. It is established that the main factor preventing the production of high-quality samples is contamination of the melt due to the gas transport reactions the growth chamber atmosphere and formation of oversaturated carbon solid solution in the Al₂O₃ matrix. The decomposition of this solid solution gives rise to the second-phase-particle precipitations. The production of highquality sapphire tubes at the growth rates up to 20 mm · min⁻¹ is possible with a careful elimination of water vapours and oxygen from the growth chamber atmosphere.     

Elastic waves in suspensions

A model of heterogeneous medium taking into account the friction between the particles and liquid, as well as the relaxation of the small-size particles to the equilibrium on the stress, has been proposed to describe the propagation of the elastic waves in a suspension. A system of wave equations describing the propagation of a plane longitudinal wave has been formulated for the components of the medium. Analytical expressions for the sound velocity in a suspension has been obtained in the approximation in which the particles are completely carried away by liquid in the limiting cases in which the particles are in equilibrium under stress with the liquid or equilibrium is absent. The dependence of the sound velocity in the medium on the volumetric portion and the size of the inclusions has been studied. The obtained results agree with the experimental data and obtained analytical expressions for the sound velocity. The dynamics of the components of the medium at the propagation of the plane longitudinal monochromatic wave has been studied.     

Surface microrelief smoothing mechanisms in a target irradiated by an intense charged particle beam

Physical mechanisms and a mathematical model are proposed to describe the smoothing of the microrelief of an irradiated surface. Before melting, smoothing is caused by elastoplastic deformation of the material; after the melting of the surface layer of the irradiated target, smoothing is caused by the dynamics of the target boundary under the action of surface tension forces, viscous forces, and inertial forces. The results of numerical simulation agree qualitatively and quantitatively with experimental data. The proposed mathematical model can be used to predict changes in the microrelief of the irradiated surface and to choose irradiation conditions when solving the problems of radiation technologies.     

Passage of a high-current relativistic electron beam through matter

A solution is presented for the problem of passage of a high-current relativistic electron beam through matter in the stationary case with one-dimensional geometry. The system of equations describing the passage of the beam consists of the kinetic equation for fast electrons, which considers the effect of the electric field on the magnitude and direction of particle momentum, the equations for the field produced by the space charge generated by thermalized electrons, and relations connecting the conductivity of the medium to the radiation field. Higher-order perturbation theory is used for the solution. The solutions reveal that the distribution of expended energy, thermalized electrons, and other properties of the flow are highly dependent on the density of the incident flux and the conductivity of the medium. It will be shown that linear transfer theory may be applied to calculation of the passage of high-current beams through matter over a wide range of currents and conductivities, if the barrier thickness does not exceed one-half the path length, but cannot be used for calculation of passage through large-thickness barriers, i.e., with thickness comparable to the electron free path length.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 67–74, September, 1979.The author thanks A. N. Didenko and A. M. Kol'chuzhkin for their evaluation of the study.     

Change in the relief of a target surface treated by compression plasma flows

The change in the surface relief of a steel-3 target (GOST 380) treated by compression plasma flows is experimentally studied. The energy density absorbed by the target varies in the range of 10–35 J/cm² and the pulse duration is 100 μs. It is shown experimentally and numerically that the development of KelvinHelmholtz instability strongly affects the formation of the target surface treated with compression plasma flows: a large-scale wave-like relief with characteristic sizes of 200 × 1000 μm is formed on the target surface and, as a result, the roughness of the surface increases. However, the microrelief at the scale of individual elements is smoothed to a maximum roughness of about 0.5 μm.     

Radiation-Induced Electrical Conductivity of Nanocomposite Materials

The radiation-induced conductivity of a nanocomposite with the inclusion of spherical nanoparticles as a function of intensity and time of action of gamma-radiation and the concentration and size of inclusions has been studied using the Rose–Fowler–Weisberg model. The energy spectrum of localized states associated with the nanoparticle inclusion has been determined. The numerical experiments have been made for polymethyl methacrylate (PMMA) nanocomposites with inclusion of CdS and α-Al₂O₃ nanoparticles as well as SrO nanoparticles.