Multibarrel Gyrotrons
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Radiophysics and Quantum Electronics, Vol. 63, No. 2, July, 2020 (Russian Original Vol. 63, No. 2, February, 2020)
MULTIBARREL GYROTRONS V. E. Zapevalov, A. S. Zuev,∗ and A. N. Kuftin
UDC 533.9.08
We propose a fundamentally new scheme of the multibarrel gyrotron. As an example, we consider three promising variants of implementation of the scheme with a generation frequency of about 140 GHz or its multiple in the case of operation at higher cyclotron harmonics. A variant of a multibarrel gyrotron with wide-range continuous frequency tuning about 13.1 GHz is discussed. The possibility of operating a gyrotron of this type at the third cyclotron harmonic with a total power of the output radiation exceeding 1 kW at a frequency of 448 GHz is considered.
1.
INTRODUCTION
A promising device in the field of high-frequency high-power vacuum electronics is the gyrotron [1, 2], which is well known as a microwave source generating high and medium power levels. Gyrotrons being representatives of cyclotron-resonance masers cover a wide frequency range (10 GHz–1 THz) and are used in a variety of applications [3–5]. For example, gyrotrons generating megawatt power levels are intensely used in nuclear fusion facilities with magnetic confinement of plasma [6]. Terahertz gyrotrons are used for diagnostics and spectroscopy of various media, diverse medico-biological applications, detection of explosives and other banned substances, and in a wide range of other uses. Of all the diversity of gyrodevices, the prevailing type is the canonical gyrotron, which consists of a magnetron injection gun that forms a tubular helical electron beam with compression in a growing strong magnetic field, an axisymmetric cavity where the electron-wave interaction takes place, a collector where the spent electron beam lands, and a radiation output system that is quasi-optical with the wave beam or axial at the operating mode. As of now, the overwhelming majority of commercial gyrotrons are canonical. However, non-canonical gyrotrons start stirring growing interest [9]. On the one hand, this is explained by the limitations of the possibilities of the traditional mode selection methods, which are sometimes insufficient to achieve stable single-mode generation, especially when operating at the gyrofrequency harmonics. On the other hand, unique properties of non-canonical gyrotrons expand significantly the potentials of the gyrotron-type devices and open up new prospects for high-frequency vacuum electronics. An example of non-canonical gyrotrons is the multibeam gyrotrons [10–14]. They were first proposed already in 1980 as a way to enhance mode selection with respect to the transverse index and increase the power of the output radiation [10, 11]. Currently, interest in such devices is rapidly growing [13–15]. As a rule, an additional electron beam is used in gyrotrons to ensure effective selection of the operating mode (see, e.g., [12]). Other variants of using electron beams in multibeam systems are also possible [13, 15]. For example, simultaneous multi-frequ
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