Chaos and hyperchaos in a gyrotron

We study oscillation in a gyrotron with allowance for reflections from an output horn. Regions with different system behaviors, such as stationary oscillation, self-modulation, and complex-dynamics regimes are found in the parameter plane. The scenarios of appearance of chaotic oscillations are considered. It is shown that they can emerge via either a sequence of period-doubling bifurcations or destruction of quasiperiodic motion. For chaotic attractors, Lyapunov exponents are calculated and their dimensions are estimated on the basis of the Kaplan-Yorke formula. The dimension values turn out to be anomalously large, which is stipulated by the presence of a large number of high-Q eigenmodes in the gyrotron cavity due to operation near the cutoff frequency of an electrodynamic system. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 887–899, October 2006.     

Wave Theory of a Traveling-Wave Tube Operated Near the Cutoff

We outline the main principles of the wave theory of interaction between an electron beam and waves in a slow-wave structure near the edge of the transmission band. Formulation of the basic equations and the boundary conditions is considered taking consistently into account that the interaction parameter is small. A comparison of the results with a discrete version of the theory is discussed. We also consider the starting conditions for the oscillation regime, the linear amplification regimes, and some effects found within the framework of the nonstationary nonlinear theory, e.g., parasitic self-excitation in the amplification regime and hard excitation of the oscillation regime.     

Influence of small polymer additives on the behavior of a linear viscoelastic fluid

A system of equations is obtained, describing a dilute polymer solution in an incompressible linear viscoelastic fluid as a nonlinear viscoelastic medium. As an example, motion with a specified velocity gradient is analyzed in the linear approximation. An expression is given for the dynamic modulus of the system in terms of the dynamic modulus of the most viscoelastic fluid containing the macro-molecules and in terms of the polymer concentration.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 3–12, November–December, 1976.     

Theoretical and Experimental Study of a Compact Planar Slow-Wave Structure on a Dielectric Substrate for the W-Band Traveling-Wave Tube

Technical Physics - A miniature planar meander-type slow-wave structure (SWS) for a W-band traveling-wave tube is studied. Computer simulation of the SWS electrodynamic parameters is performed. A...     

FDTD-analysis of the wave diffraction from dielectric waveguide discontinuities

The problem of the guided mode reflection from the planar dielectric waveguide end is studied by the finite difference time domain method. The influence of facet deformations on the scattering characteristics is considered. The reflectivity problem for the system with the nonlinear dielectric waveguide insert is examined.     

Finite-Element Model of a Fiber-Optic Polarizer

Numerical analysis of the vector modes of a fiber-optic polarizer is performed by the finite-element method. The calculation results are compared with the data obtained using a planar model.