Гиротрон

Topic. The paper is devoted to the study of mutual synchronization of two gyrotrons coupled with delay. As a rule, a theoretical study of synchronization of gyrotrons and other microwave oscillators is usually carried out by numerical simulations using certain well-established models of microwave electronics. Using this approach, it is difficult to provide a fairly complete synchronization pattern, using methods and ideas of nonlinear dynamics.

The investigation of operation regimes of CW/263 GHz/1kW gyrotron, developed at IAP RAS/GYCOM Ltd., was made by various numerical methods. The influence of the azimuthal inhomogeneity (such as electron beam radial misalignments and tilt) has been studied. The method of average equations and 3D PIC codes (CST Studio Suite and KARAT) were used. Results, achieved by different methods, are in agreement with experimental data.

We study gyrotron frequency locking by the external monochromatic wave and stabilization of gyrotron frequency by the wave reflected from the non-resonant or resonant load. Although in the last decades influence of the external monochromatic signal and the reflected wave at the gyrotron operation was studied in a number of publications, concrete schemes of gyrotron frequency stabilization weren’t discussed.

The simulation technique of helical beam formation system of gyrotrons with typical axial symmetry distortion is presented. The simulation of the second harmonic magnetron-injection gun for 260 GHz band gyrotron with 0.5 mm beam axis displacement was made. It was shown that displacement of axis beam has a significant effect upon the angular distribution of pitch-factor.

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The paper presents the results of research is carried out in the Institute of Applied Physics and is aimed at creating a CW submillimeter gyrotrons with an output power of several tens of watts. Results of experiments on the 258 GHz gyrotron at the second harmonic of the gyrofrequency are presented. In the course of experiments maximum output power of 200 W and the relative stability of the output frequency at 5 · 10−6 for the hours-long continuous operation of the gyrotron were achieved.

In a gyrotron with quasi­optical mode convertor, apart from the fundamental mode, excitation of a mode with opposite azimuthal rotation of the field occurs due to the wave reflected from the remote load. Interaction of the two oppositely rotating modes is investigated by using the quasi­linear equation for slowly varying amplitudes. The developed theory allows explanation of the experimental results where periodic modulation of the transverse structure of gyrotron radiation partially reflected from a remote oscillating membrane was observed.

Effect of reflection from the remote load on the mode competition in a two-mode electronic maser is considered. A system of quasilinear equations for slowly varying amplitudes of the modes with cubic nonlinearity where the effect of reflections is taken into account by time delayed terms is analyzed. The most typical case of competition of two modes with close frequencies at the centre of generation zone is studied in detail. Change of generation regimes with increasing of reflections of the spurious mode at different values of delay is investigated analytically and numerically.

During numerical simulations of the model of gyrotron with fixed field-structure, zones of stable single-mode generation of the work mode are analyzed on the plane of parameters «magnetic field – beam current». It is shown that area and sizes of the zones are strongly dependent on the spectral density of eigen-frequencies of the resonator and on number of considered parasit modes. With increase of spectral density the point of highest attainable efficiency of stable single-mode generation shifts to the region of lower currents and simultaneously this value of efficiency decreases.