The wave dispersion in the slow-wave structure such as a coaxial ribbed line has been analyzed. For the case of the excitation of an axially symmetric wave in this structure, the generalized dispersion equation has been obtained using the method of sewing the conductivities. The particular cases of a solution of the dispersion equation have been analyzed, as well as its solutions for relatively high and low frequencies, since these cases are of practical interest. The parameters of a coaxial ribbed line have been simulated and the dependences of the slowing coefficient and the wave impedance of the structure on its geometrical dimensions have been obtained.
The terms of the quasimolecule Ne(2p{sup 5}3S)-H{sub 2} are calculated by the pseudopotential method. It is shown that the potential surfaces for all the states of Ne(2p{sup 5}3S)-H{sub 2} are almost identical (in the region accessible to thermal collisions) and depend weakly on the orientation of the H{sub 2} molecule. The autoionization widths of resonantly exacted quasimolecular states Ne(3s{sup 1,3}P{sub 1}) with H{sub 2} and D{sub 2} molecules are presented in the form of a sum of calculated contributions of the direct ionization mechanism and of the exchange mechanism, which are expressed in terms of experimental cross sections and constants for metastable Ne(3s{sup 3}P{sub 0,2}) atoms. The ionization rate constants obtained at T = 300 K agree with existing experimental data. It is shown that for the collisions Ne(3s{sup 1}P{sub 1}) + H{sub 2}, D{sub 2} the ionization process is governed by the direct mechanism, since the values calculated by taking only this mechanism into account provide good estimates for the cross section and the ionization rate constant. For the collisions Ne(3s{sup 3}P{sub 1}) + H{sub 2}, D{sub 2} the ionization process is governed by the exchange mechanism and the cross sections (constants) are close to the corresponding values formore » metastable atoms Ne(3s{sup 3}P{sub 0,2}). The diffusion coefficients of the excited atoms Ne(3s{sup 1,3}P{sub 1}) in molecular hydrogen and deuterium are also calculated. 34 refs., 6 figs., 1 tab.« less
An algorithm is developed for numerical solution of the two-dimensional problem of scattering of an E-polarized field by a dielectric cylinder in a plane-layered medium. Plane-wave scattering by a cylinder imbedded in a homogeneous dielectric layer with rectangular and rhombic cross-sections is studied.
Three novel methods are described for producing electron beams with energies of hundreds of keV. In the first method, an intense electron beam hits a lead target. The initial portion of the beam vaporizes the lead to form a gaseous target that scatters the rest of the beam, thereby generating a beam of polarized electrons. In the second method an electron beam is passed through a beam of polarized hydrogen atoms. The polarized electrons formed by ionization are confined in an electrostatic trap until the current pulse of the ionizing beam ends, after which they are extracted by voltage pulses. In the third method the electrons accumulate on the surface of a dielectric in a magnetic field. After the spins have relaxed, the electrons are removed from the surface by an electric field. Calculations and preliminary experiments indicate that these methods can be used to generate polarized electrons with beam currents of several hundred mA in a pulse of duration {approximately}1 {mu}s, with degree of polarization {approx}40% in the first method and nearly 100% polarization in the second and third methods. 12 refs., 6 figs., 1 tab.
Qualitative arguments and quantitative estimates are given concerning the use of rf quadrupole focusing in proton linacs at energies above 100 MeV. Radio-frequency quadrupole focusing is widely used in ion foreinjectors in linear accelerators to form and preaccelerate ion bunches to velocities of 0.06 to 0.08. Some success has been reported in the use of rf quadrupole focusing to accelerate protons to 30 MeV.
The penetration of channeled electrons through an area distorted by an edge or screw dislocation is considered. It is shown that this process may be described in the approximation of a sharp shift of atomic rows and planes, which leads to dechanneling about 30% of particles passing through the distorted area. The maximum length of dechannelling in a dislocated crystal and the threshold electron energy, above which the dechannelling length decreases with increase in the energy, was established. Approximate estimates of these values for silicon and tungsten were also received. Proceeding from the carried out analysis of the microscopic pattern of channelled particles passing through dislocations, the principle of detailed balance was considered, and a general transport equation, describing also dechanneling by dislocations besides the usual multiple scattering, was formulated.
