Characteristics of electron beams formed in a diode with magnetic insulation

The problems of the formation of relativistic electron beams in a cylindrical diode with an annular cathode are discussed in the approximation of an infinitely strong guiding magnetic field. The beams are treated as infinitely thin. The following cases are investigated: 1) The formation of an electron beam moving off the cathode with an initial velocity. The case in which the field on the cathode is not equal to zero is investigated. It is shown that the potential of the electron beam can be determined in a nonunique fashion in the drift region. 2) The formation of a two-velocity electron beam. The possibility of controlling the flow of kinetic energy of the beam by varying the fraction of fast electrons in it is shown. 3) The formation of an electron beam in a diode with the help of two opposed cathodes at different potentials. A strong dependence of the current in the diode on the potential difference between the cathodes is obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 36–39, December, 1981.     

Dynamic aspect of solid solution cathodes by method of integral transform

A mathematical model is presented for a thin film, spherical and cylindrical particles electrodes under galvanostatic discharge. The model available to simulate the electrochemical behavior is discussed considering not only their electrochemical representation (transport phenomena), but also the mathematical techniques, i.e. Integral transform that have been used for solving the equations. We examine the non-homogeneous material balance equation in the rectangular, spherical and cylindrical coordinate system; determine the elementary solutions, the norms and the eigenvalues of the problems for galvanostatic boundary conditions and systematically tabulate the resulting expressions. Expressions are developed for plane, cylindrical and spherical particles giving the relation between battery load and the amount of cathode material utilized. The particle shape and a single parameter Q is used to describe cathode performance.     

Thin charged shells and the violation of the third law of black hole mechanics

The collapse of an infinitely thin spherical shell of charged matter, which surrounds a spherically symmetric black hole or has a flat interior, is analyzed in connection with the laws of black hole mechanics and the cosmic censorship hypothesis. An effective potential is introduced to describe the motion of the shell. The process, proposed by Farrugia and Hajicek as a counterexample to the third law, is discussed and generalized to the case of nondust shells.     

Nonlinearity of solids with micro- and nanodefects and characteristic features of its macroscopic manifestations

The meaning of the experimentally measured nonlinear parameters of a medium is discussed. The difference in meaning between the local nonlinearity, which is measured in the vicinity of a single defect and depends on the size of the region of averaging, and the effective volume nonlinearity of the medium containing numerous defects is emphasized. The local nonlinearity arising at the tip of a crack is calculated; this non-linearity decreases with an increase in the region of second harmonic generation. The volume nonlinearity is calculated for a solid containing spherical cavities. The volume nonlinearity is also calculated for a medium containing infinitely thin cracks in the form of circular disks, which assume the shape of ellipsoids in the course of the crack opening. The nonlinear acoustic parameter is calculated with the use of the exact classical results of the theory of cracks.     

Acceleration of a multicomponent plasma in the cathode region of a vacuum arc

A general solution to the problem of the steady-state spherical expansion of a current-carrying multicomponent plasma into a vacuum is derived. It is shown that, in vacuum arc discharges, the main force accelerating the cathode material, which becomes a plasma at distances of 1 to 300 μm from the cathode surface, is the electron pressure gradient force maintained by Joule heating. It is established that ions of different charges move with the same hydrodynamic velocity, which is uniquely determined by the mass and mean charge of the ions and the maximum electron temperature in the cathode region.     

Emissionsmikroskopische Messung der Ortsverteilung von 20 keV-Elektronen nach Streuung in dünnen Al- und Ge-Aufdampfschichten

Electrons incident on a thin film are displaced laterally when leaving the target by elastic and inelastic scattering. The widening of the current density distribution of an electron beam with an initial energy of 19.5 keV and an initial Gaussian distribution with a half width of about 0.6 microns by plural and multiple scattering as well as in the region of complete diffusion (corresponding to mass thicknesses ranging from 40–500 µg/cm²) is measured for evaporated films of Al and Ge. From these results the increase in half width of an infinitely fine primary electron beam (δ-function response) is computed and plotted. In order to measure the current density distribution of the scattered electrons it is converted to an equivalent distribution of secondaries using a cathode lens image converter. These distributions are magnified and scanned electronically or recorded photographically.     

Effect of Nozzle Geometry on the Rewetting of Hot Surface During Jet Impingement Cooling

An investigation has been carried out to investigate the effect of nozzle geometry on hot horizontal surface rewetting during water jet impingement cooling. The test surface of 800 ± 10°C initial surface temperature is cooled by water jet of 22 ± 1°C temperature. The water flow is varied to maintain the jet Reynolds number in a range of 5,000 to 24,000. The rewetting phenomena with sharp-edged and tube-type nozzles are compared on the basis of rewetting temperature, wetting delay, rewetting velocity, and maximum surface heat flux. The rewetting performance with tube-type nozzle is better than the sharp-edged nozzle particularly for the downstream spatial locations; however, maximum surface heat flux at the stagnation region is higher with the sharp-edged nozzle.     

On the calculation of the classical Liouville operator for the step-type interparticle interaction

A new method of the determination of the Liouville operator for the step-type interparticle interaction is presented. The interaction part of the Liouville operator is calculated for the particles interacting via a spherical repulsive and spherical attractive barrier. Limiting cases of an infinitely high (hard core) and infinitely deep barrier are discussed. These results can be used for the determination of the interaction part of the Liouville operator for an arbitrary step-type interaction which can be expressed as a sum of several attractive and repulsive barriers.     

Spectroscopy of Zinc Oxide Thin Films near the Fundamental Absorption Edge

Optics and Spectroscopy - The optical absorption spectra of zinc oxide (ZnO) thin films formed by reactive cathode sputtering are studied. The observed absorption of light in the region of photon...     

The Influences of the Magnetic Field Strength on the Magnetic Confinement of Primary Electrons in an Ion Source

This paper deals with the simulation of trajectories of energetic electrons under the influence of a multi-cusp magnetic field produced by a permanent magnet assembly in a ring cusp geometry which is designed for supporting a plasma based ion source. The primary electrons are assumed as being emitted from a cathode located coaxially with the cylindrical discharge chamber. The volume of the region occupied by the electron trajectories and the magnetic trapping time were evaluated and plots are presented showing the effects of the surface magnetic field strength of the magnets on the volume and the mean confinement time of primary electrons in the ion source.     

电磁复合聚焦—偏转球面阴极透镜的相对论象差理论

本文应用变分原理研究了电磁复合聚焦-偏转球面阴极透镜的相对论象差理论。在考虑阴极面逸出电子具有一定的初能量和初角度分布,物场和象场弯曲以及阴极面上磁场和横向电场不为零的情况下,导出了任意理想象面上的一级近轴横向象差和包括色球差在内的全部三级几何横向象差,以及各种特殊类型象差系数的明显表达式。本文导出的象差公式不仅普遍适用于宽束和细束阴极透镜,而且普遍适用于相对论或非相对论,阴极和屏为球面或平面时的各种情况。本文以复数描写轨迹,用矩阵表示象差,形式简洁,适合于计算机计算。 关键词：     

Gravastars and black holes of anisotropic dark energy

Dynamical models of prototype gravastars made of anisotropic dark energy are constructed, in which an infinitely thin spherical shell of a perfect fluid with the equation of state p = (1 − γ)σ divides the whole spacetime into two regions, the internal region filled with a dark energy fluid, and the external Schwarzschild region. The models represent “bounded excursion” stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes. Here we show, for the first time in the literature, a model of gravastar and formation of black hole with both interior and thin shell constituted exclusively of dark energy. Besides, the sign of the parameter of anisotropy (p _t − p _r ) seems to be relevant to the gravastar formation. The formation is favored when the tangential pressure is greater than the radial pressure, at least in the neighborhood of the isotropic case (ω = −1).     

Position-space description of the cosmic microwave background and its temperature correlation function

We suggest that the cosmic microwave background (CMB) temperature correlation function C(theta) as a function of angle provides a direct connection between experimental data and the fundamental cosmological quantities. The evolution of inhomogeneities in the prerecombination universe is studied using Green's functions in position space. We find that a primordial adiabatic point perturbation propagates as a sharp-edged spherical acoustic wave. Density singularities at its wave fronts create a feature in the CMB correlation function distinguished by a dip at theta approximately 1.2 degrees. Characteristics of the feature are sensitive to the values of cosmological parameters, in particular to the total and the baryon densities.     

Effect of space charge and the initial electron velocity on the potential distribution in a plane diode

The problem of the potential distribution in a plane vacuum diode is solved for arbitrary values of the space charge density and the initial electron velocity. The resultant solution makes it possible to study the conditions for the potential minimum appearing near the cathode, to determine the position and depth of this minimum, to derive analytic formulas for the potential distribution in the entire space between the cathode and the anode, and to analyze the problem of an infinitely high space charge density.     

Large-Scale Two-Dimensional Quantum Fluctuations of Five-Dimensional and Four-Dimensional Space-Time Metrics

Large-scale two-dimensional quantum fluctuations of five-dimensional space-time metric are constructed and the effect of the fluctuations on the nested four-dimensional worlds is studied. In doing so, the fluctuations affect not all four-dimensional worlds but only a part of them. The energy-momentum tensor of four-dimensional space-time has a physical form both in the absence and in the presence of fluctuations; it means that the fluctuations can be realized by real matter. A spatial region occupied by the fluctuations constructed in this work can be infinitely large and the fluctuations can occur during a long period of time. Therefore, we refer to these fluctuations as large-scale fluctuations.     

Thermally and optically induced effects on sub-band gap absorption in nanocrystalline CdSe (nc-CdSe) thin films

Nanocrystalline cadmium selenide (nc-CdSe) thin films have been prepared by thermal evaporation using the inert gas condensation (IGC) technique. Transmission electron microscopy (TEM) studies show that the CdSe nanocrystals (NCs) are spherical in shape. Constant photocurrent method (CPM) is used to determine the value of absorption coefficient in low absorption region of as-deposited, annealed and light soaked nc-CdSe thin films. Values of optical band gap (E_g) have been determined by using Tauc's relation for as-deposited, annealed and light soaked nc-CdSe thin films from the α values evaluated from reflection and transmission measurements. We have used a derivative procedure to sub-gap absorption spectra in order to get information on the energetic distribution of the occupied density of states below Fermi level. Constants such as optical gap E_g, Urbach edge E_u have been obtained from CPM spectra in as-deposited, annealed and light soaked nc-CdSe thin films. Concentration of defect states has also been calculated in as-deposited, annealed and light soaked nc-CdSe thin films.     

Parameters of the Kinetic Layer of Arc-Discharge Cathode Region

The model is presented and the equation system is obtained which describes the nonequilibrium (Knudsen's) region of a cathode jet at the arc discharge burning in vapors of electrode material. The nonequilibrium layer is formed as a result of streaming of cathode-erosion products in the medium with reduced pressure and presents the discontinuity surface of the hydrodynamical region. The equation system was obtained by analyzing the law of conservation of heavy particles in the layer. Calculation results are presented and parameters of a cathode jet in the kinetic layer are discussed. It is shown that this flow is not a free one and its parameters are dependent on energy release in the near-cathode region.     

Stability of the normal phase in a bounded current-carrying superconducting film

The two-phase equilibrium states of a current-carrying thin superconducting film in the case of convective heat transfer on the free surface are considered, and their stability is investigated in a first approximation. It is shown that of the two equilibrium states, the state with the normalphase region of larger size is stable. In the limiting case of an infinitely long film, the stable two-phase equilibrium state tends to a spatially uniform normal state, and the unstable state remains localized. In a definite range of values of the system parameters, the relaxation time of such a formation can be fairly long, and it should be regarded as a quasistable equilibrium state. Zh. Tekh. Fiz. 68, 71–77 (June 1998)