UDC 621.385.624
3D modelling of gain
processes in multibeam klystrons
R. V. Egorov, V. L. Savvin
M.V.Lomonosov Moscow State University, Faculty of Physics,
Leninskie Gory, 1-bl.2, Moscow 119991, Russia
The paper is received on May 23, 2019
Abstract. Three-dimensional
modeling of electronic processes in powerful multibeam klystrons was performed
for the first time, caused by the need for detailed analysis of the
amplification processes. The main purpose of the simulation was to identify the
main physical factors limiting the efficiency of signal amplification in multibeam
structures, rather than optimizing the parameters of a particular klystron in
order to achieve maximum efficiency. The 40-beam nine-resonator BAC – klystron with
an electron beam power of 10.4 MW, operating at a frequency of 2.99 GHz. was chosen
as prototype of the model. The results of the three-dimensional simulation of
amplification processes showed that beams in different channels propagate differently
and calculation of output parameters of multibeam klystrons cannot be performed
by "mechanicaly" multiplication of optimized results obtained in
single-beam programs by the number of beams.
The results
obtained gave a possibility to observe a three-dimensional "picture"
of electronic processes in a multibeam klystron for the first time, although
the calculated efficiency values differed from the experimental values. This is
due to the fact that during simulation a constant level of the external
focusing magnetic field 850 GS was used. In the experiment, the value of the
magnetic field increased along the device from 850 up to 1350 Gs. Therefore, in
the simulation, the electron bunches were less compact before the entrance of
output resonator decreasing the final efficiency.
In addition, the
simulation demonstrated that the input loop reduces the amplitude of
high-frequency fields and characteristic resistance in the channels of the
input resonator, causing a significant difference in the amplitude of the
electric field of the main mode in different channels. Therefore, the electrons
in the channels located near the power input are grouped worse and experience
weaker braking in the output resonator. In the experimental prototype these disadvantages
have been eliminated "manually" by tuning of the resonator. Thus, the
results of the three-dimensional simulation of multibeam klystron showed that
amplification processes occur in different ways at different channels, the
distribution of the microwave field is non-uniform, the asymmetry of the input
and output coupling devices has a noticeable effect, as well as the higher
modes of oscillations in the used oversized resonators.
Key
words: multibeam klystrons,
three-dimensional modeling, grouping.
References
1.
R. V.
Egorov, I. A. Guzilov, O. Y. Maslennikov. Pulsed 6 MW BAC multiple-beam
klystron. Zhurnal Radioelektroniki - Journal of Radio Electronics,
2017, No. 7. Available at http://jre.cplire.ru/jre/jul17/3/text.pdf. (In
Russian)
2. R. V. Egorov, I. A. Guzilov, O. Y. Maslennikov, V. L. Savvin. About
possibilities of increasing the output power of BAC klystrons. Zhurnal
Radioelektroniki - Journal of Radio Electronics, 2017, No. 10. Available
at http://jre.cplire.ru/jre/oct17/12/text.pdf.
(In Russian)
3.
R. V. Egorov, I. A.
Guzilov, O. Y. Maslennikov, V. L. Savvin. BAC-Klystrons: A New Generation of Klystrons in Vacuum
Electronics. Moscow University Physics Bulletin,
2019. Vol. 74, No.1, P. 38-42.
4. Konnov A.V., Malykhin A.V. Frequency-domain
code Dev. 5.1 for analysis of coupled cavity traveling wave tubes, klystrons
and their hybrids. Proc. IVEC. 2005,
Noordwijk, Netherlands, pp. 195-198.
For citation:
R.V. Egorov, V. L.
Savvin. 3D modelling of
gain processes in multibeam klystrons. Zhurnal
Radioelektroniki - Journal of Radio Electronics. 2019. No. 6. Available at http://jre.cplire.ru/jre/jun19/1/text.pdf
DOI 10.30898/1684-1719.2019.6.1