UDC 537.87
Nonlinear
Dynamics of Multimode Gyrotron under the Influence of External Quasi-Monochromatic
Signal
V. L. Bakunin,
G. G. Denisov, Yu. V. Novozhilova
Institute
of Applied Physics Russian Academy of Sciences, Ulianov str., 46,
Nizhny Novgorod 603950, Russia
The
paper is received on November 15, 2019
Abstract. The possibility of controlling the
radiation frequency of a powerful multimode gyrotron under the influence of an
external signal with a harmonically varying frequency or amplitude, as well as
two monochromatic signals, has been theoretically studied. These tasks are important
for various practical applications, such as suppressing plasma instabilities in
tokamaks and stellarators, spectroscopy, as well as creating a complex of
coherently emitting gyrotrons in the future. The conditions are found when the
frequency and phase of the operating mode are locked by an external signal. In
this case, generation occurs at the operating mode with a periodically changing
frequency and amplitude. The regimes observed at the exit from the locking
zones are investigated. The calculations were carried out on the example of a
megawatt power level gyrotron developed at IAP at a frequency of 170 GHz with
an operating mode TE28,12.
When the gyrotron is exposed to an
external signal with a harmonically changing frequency close to the frequency
of the operating mode, the frequency of this mode can be locked. The frequency
control are possible if the changes in the frequency of the external signal are
quite slow compared to the locking time, and the instantaneous frequency of the
external signal lies within the locking band at all times. If the frequency of
the external signal leaves the locking band, beating of the operating mode or
excitation of spurious modes occur.
Under the influence of an
amplitude-modulated signal with a harmonically changing amplitude or two
monochromatic external signals, periodic changes in the frequency and amplitude
of the operating mode occur with a period of signal amplitude modulation. If
the beat of the amplitude of the external signal is rather deep and slow in the
locking time scale, and if there are no free-running single-mode operation for
the specified gyrotron parameters, decay into spurious modes takes place. If
the amplitude fluctuations are sufficiently small, the parasitic modes are not
excited.
When changes in the frequency and
amplitude of the external signal are rapid in the locking time scale, parasitic
modes are not excited, because the amplitude and frequency of radiation do not
have time to track changes in the parameters of an external signal and
fluctuate in a small range of values.
Key words: multimode gyrotron, nonlinear mode
competition, frequency locking, spectrum control.
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For
citation:
Bakunin V.L., Denisov
G.G., Novozhilova Yu.V. Nonlinear dynamics of multimode gyrotron under the influence
of external quasi-monochromatic signal. Zhurnal Radioelektroniki - Journal
of Radio Electronics. 2019. No. 12. Available
at http://jre.cplire.ru/jre/dec19/1/text.pdf
DOI 10.30898/1684-1719.2019.12.1