A.A. Bogdashov – Senior Research Scientist, 
Institute of Applied Physics of RAS (N. Novgorod)
E-mail: bogdash@ipfran.ru

M.Yu. Glyavin – Head of Laboratory, 
Institute of Applied Physics of RAS (N. Novgorod)
E-mail: glyavin@appl.sci-nnov.ru

Yu.V. Novozhilova – Senior Research Scientist, 
Institute of Applied Physics of RAS (N. Novgorod)
E-mail: julia.novozhilova2009@yandex.ru

A.S. Sedov – Research Scientist, 
Institute of Applied Physics of RAS (N. Novgorod)
E-mail: anton-sedov@mail.ru

A.P. Fokin – Research Scientist, 
Institute of Applied Physics of RAS (N. Novgorod)
E-mail: ap.fokin@mail.ru

The paper presents the results of a series of model experiments devoted to the effect of a signal reflected from a nonresonant load on the operation regime of a technological gyrotron. The nonresonant reflector used in the experiments was an annular diaphragm with remote control of its position in the waveguide. The possibility of frequency tuning in the band determined by the quality factor of the gyrotron resonator and power modulation in range up to 20% was demonstrated in the experiment.

Recently, interest in tasks related to the control and stabilization of the frequency in gyrotrons of various frequency ranges and power levels has increased significantly. Development of ways to control the output power and frequency will open up new prospects for the use of gyrotrons in many applications, such as plasma diagnostics or spectroscopy. At present, various approaches to the problem of controlling and stabilizing the frequency and power are being considered. Available methods can be divided into two large groups. The first group is the active methods of automated control of electron beam parameters (accelerating or modulating voltage, magnetic field) or parameters of the gyrotron resonator. Active methods include such well-established approaches as phase-locked loop, which provide a record frequency stability and spectrum width, but require the use of a number of additional devices, in particular, highly stable reference oscillators.

The second group includes passive methods based on the effect of an external signal or a reflected wave on the operation of the gyrotron. To implement these methods, no changes in the design or power supply are required, but for locking by an external signal, a microwave source with a power level of several percent of the power of the gyrotron is required. Therefore, methods based on the reflection of a signal from a remote load are much more accessible.

The paper presents the results of experiments on the effect of a signal reflected from a remote nonresonant load on the generation regime of a 28 GHz technological gyrotron. The possibility of a twofold decrease in the sensitivity of the gyrotron radiation frequency to oscillations of the technical parameters of the installation, such as the magnitude of the magnetic field or accelerating voltage, has been demonstrated. A method of smooth control of the power and frequency through the use of a movable non-resonant reflector is proposed.

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