"JOURNAL OF RADIO ELECTRONICS" (Zhurnal Radioelektroniki ISSN 1684-1719, N 6, 2019

contents of issue      DOI  10.30898/1684-1719.2019.6.1     full text in Russian (pdf)  

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