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The effect of shielding an electron source from a homogeneous external magnetic field of the drift chamber on the nonlinear dynamics of the electron beam with a virtual cathode (VC) and on the characteristics of output microwave radiation in a low-voltage vircator have been numerically simulated within the framework of a two-dimensional model. It is established that the increased degree of shielding of the electron source from the external magnetic field leads to the complication of the VC dynamics in the system and the corresponding chaotization of the output microwave radiation. Physical processes that account for the observed effect of shielding are analyzed. [ABSTRACT FROM AUTHOR]

The possibility of a continuous feedback control of chaos in an electron beam with supercritical current is considered within the framework of a hydrodynamical model of the Pierce diode. A method for controlling chaotic dynamics through stabilization of an unstable equilibrium state in a distributed active medium is proposed. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A new scheme of an effective ultralow-voltage generator of broadband chaotic microwave oscillations is considered. The device operates on counterpropagating turbulent electron beams, one of which is created by a secondary-emission cathode. Results of an experimental investigation of the device prototype operating in various regimes are summarized. Promising features of the proposed ultralow-voltage oscillator are the relatively low accelerating voltages (below 500 V), increased efficiency (up to 14-15%) compared to analogs, broad band of generated oscillation frequencies, high level of integral output power (up to 35 W), the possibility of fast and easy control over the generation regimes (from almost monochromatic to broadband), and small dimensions of the device. [ABSTRACT FROM AUTHOR]

The new scheme of an ultralow-voltage generator of broadband chaotic microwave oscillations is considered, which operates on counterpropagating turbulent electron beams. Results of an experimental investigation of the device prototype operating in various regimes are summarized. Promising features of the proposed ultralow-voltage oscillator are the relatively low accelerating voltages (500-600 V), high efficiency (up to 8%), broad band of generated oscillation frequencies, high level of integral output power (up to 20 W), possibility of fast and easy control over the generation regimes (from almost monochromatic to broadband), and small dimensions of the device. [ABSTRACT FROM AUTHOR]

We have studied the effect of dissipation on the development of instability in a superthreshold electron beam. The instability is related to an aperiodic modulation of the beam current density in a medium with negative dielectric permittivity. It is shown that the dissipative instability increment in a superthreshold electron beam depends on the dissipation level stronger than in a subthreshold beam. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]