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The linear and nonlinear theory of a plasma-filled relativistic Cerenkov generator with coaxial slow-wave structure (SWS) is developed. Linear analysis includes the space-charge limiting current, dispersion relations, dispersion curves, and coupling impedance. In nonlinear theory, the electron beam space-charge effect, nonsynchronous interaction, and complex reflection coefficients of the electromagnetic wave at the boundaries of the SWS are taken into account. With the assumption of quasi steady state, the self-consistent equations are numerically calculated using the fourth-order Runga-Kutta method. The effects of the relative phase between inner and outer corrugations, phase and amplitude of the complex reflection coefficient at the boundaries of the SWS, and plasma density on device efficiency are discussed. Efficiencies of up to 37% without plasma and about 59% with plasma density of np = 3-7 × 1011 cm-3 are obtained. [ABSTRACT FROM AUTHOR]

A klystronlike relativistic backward wave oscillator (RBWO) with a dual-cavity extractor is presented. The phase of the axial electric field component Ez varies by 0° in the dual-cavity extractor, and a larger electric field appears in the second extraction cavity, in comparison with a single-cavity extractor. Such an improved field distribution is beneficial for converting modulated beam power into microwave power. The particle in cell simulation results reveal that microwaves with power of 10 GW, frequency of 4.3 GHz are generated, and conversion efficiency is 48% when diode voltage is 1.2 MV and beam current 17.3 kA. [ABSTRACT FROM AUTHOR]