[en] The authors study the possibility of open-quotes invertingclose quotes the operation of a Cerenkov FEL into an electron accelerator device driven by X-band microwaves that propagate in a slow-wave TM mode (axial E-field). The waveguide may be rectangular, with slabs of dielectric material located parallel to and along the walls, well separated from the electron beam; or possibly cylindrical. Tapering of the axial wavenumber of the mode, using the guide width and or dielectric filling factor, will maintain an accelerating electron in Cerenkov resonance. By using a few psec pulse of electrons from an rf gun (γ = 9), the electrons are injected into a narrow window of accelerating phases. Because of the smooth bore structure, absence of a guiding magnetic field, and its one-dimensionality, the MICA is likely to have good transverse emittance. A set of first order accelerator equations with self-consistent radiation fields has been derived; numerical examples appropriate for a laboratory accelerator having an output beam energy of several MeV will be presented

[en] A non-linear analysis of a Cerenkov maser is presented. The system consists of a ring configuration of a cylindrical waveguide filled with a dielectric material. A single transverse-magnetic mode is assumed to propagate in the system. A low-density pencil electron beam travels in part of the ring, confined by a strong axial magnetic field. Using the single-particle description for the beam and the wave equation for the field, we obtain a set of two coupled non-linear differential equations describing the slowly varying amplitude and phase of the electromagnetic mode. The gain per path is assumed to be small and the spatial growth of the field is neglected. The resulting time dependent amplitude includes the exponential gain of the linear stage and the saturation to its maximum value. The time dependent frequency is also calculated. The two equations are combined to a single Van Der Pol equation with a non-linear restoring force. This description demonstrates the similarities and differences between the Cerenkov maser and other lasing systems

No abstract available

[en] The spontaneous emission by ballistic electrons which transverse a superlattice yields as many as 5 sm-bullet 10⁸/sec IR photons for an injected current of 100 μA into a 5 x 20 μm² device. Based on this result the authors obtain the rate of stimulated emission and the gain of an electromagnetic wave. They find that the threshold current density for net wave amplification is about 10⁴A/cm²

No abstract available

[en] A Smith-Purcell oscillator with a thick electron beam is analyzed in its exponential gain regime. A threshold current less than 1[A] is found for a 1 mm wavelength; this threshold is much lower than that of a similar oscillator operating in a linear gain regime

[en] Highlights: • Optical constants of flexible plastic substrates including PMMA, COC, PET, PEN, and PI substrates. • Classification of birefringent plastic substrates using Mueller matrix spectroscopic ellipsometry data. • Full 16 Mueller matrix measurement and analysis strategy for optically biaxial plastic substrates. - Abstract: This work reports on Mueller matrix spectroscopic ellipsometry characterization of various flexible plastic substrates that are optically anisotropic with varying degrees of birefringence. The samples are divided into three groups according to the suggested characterization strategy: low birefringence, high birefringence, and twisted birefringence. The first group includes poly(methyl methacrylate) and cyclic olefin copolymer substrates. These are modeled with biaxial anisotropy for the real part of the refractive index while the imaginary part is approximated as isotropic due to small light absorption. The second group includes polyethylene terephthalate and polyethylene naphthalate substrates, which are modeled with biaxial anisotropy for both real and imaginary refractive indices. Lastly, a polyimide substrate is described as two birefringent layers with twisted in-plane orientation.

[en] The thermoelectric power of the high temperature conductive phase of V₆O₁₃ was measured and its variation with temperature is explained in terms of a simple model. The model assumes a narrow band for the d' electrons and the Seebeck coefficient is calculated in the atomic limit of the narrow band. The only fitting parameter of the theoretical expression is U - the effective Coulomb repulsion between two electrons occupying the same site. Very good agreement between theory and experiment was obtained for U = 0.075 eV. (author)

[en] The neutrino transport equation is nonlinear due to the Pauli exclusion principle. Enhanced absorption and spectrum hardening are typical phenomena stemming from this nonlinearity. The numerical methods used for the solution of the linear neutron transport equation were applied to the nonlinear neutrino transport equation. The sensitivity of the total energy leakage to the numerical parameters of a sample problem is presented in detail

[en] When a plasma is extremely dense or hot, the electrons lose their efficiency for stopping heavy charged particles. The main process for their slowing down then is the small-angle ion-ion scattering, where the bare Coulomb cross section becomes infinite as theta^-4. The purpose of this paper is to evaluate the collective screening effects which make the ion Coulomb cross section finite. The calculations are performed in the random-phase approximation and show that the Coulomb cross section is essentially cut off for energy transfers smaller than h ω/subp/, where ω/subp/ is the plasma frequency of the ions