Low operating voltage is highly attractive for medium-power millimeter-wave gyrotrons since it can reduce their size and cost, increase their safety, and, thus, improve usability for applications. However, at low voltages, the voltage depression caused by DC space-charge fields significantly limits the electron current and transverse power in the beam. Moreover, this current limitation is more pronounced for a beam with a higher pitch factor. As a result, for a given anode voltage, there is a pitch factor at which the transverse beam power in the gyrotron cavity is the maximum. This ultimate transverse power is found analytically in the non-relativistic approximation. Such a power is reached when the pitch factor calculated without taking into account voltage depression is only 0.82; voltage depression decreases the axial electron velocities, thus, increasing the actual pitch factor value in the cavity up to 1.4. As a result of this effect, high power and high efficiency cannot be obtained simultaneously in a low-voltage gyrotron. Using particle-in-cell simulations, two variants of low-voltage (5 kV) gyrotrons have been designed, namely, a device with higher power and an optimal pitch factor of 0.82 in the cavity and a device with a high pitch factor and high efficiency, but lower power.
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September 2022
Research Article| September 19 2022
Ultimate transverse power of pulsed low-voltage gyrotron beam
Dun Lu
;
Dun Lu
(Investigation, Methodology, Writing – original draft)
1
Terahertz Science and Technology Key Laboratory of Sichuan Province, School of Electronic Science and Engineering, University of Electronic Science and Technology of China
, Chengdu 610054,
China
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Wenjie Fu
;
Wenjie Fu a)
(Funding acquisition, Investigation, Methodology, Supervision, Writing – review & editing)
1
Terahertz Science and Technology Key Laboratory of Sichuan Province, School of Electronic Science and Engineering, University of Electronic Science and Technology of China
, Chengdu 610054,
China
a)Author to whom correspondence should be addressed: fuwenjie@uestc.edu.cn
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Alexey Fedotov
;
Alexey Fedotov
(Formal analysis, Investigation, Writing – review & editing)
2
Institute of Applied Physics of the Russian Academy of Sciences
, Nizhny Novgorod 603950,
Russia
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Mikhail Glyavin
;
Mikhail Glyavin
(Resources, Supervision)
2
Institute of Applied Physics of the Russian Academy of Sciences
, Nizhny Novgorod 603950,
Russia
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Mikhail Proyavin
;
Mikhail Proyavin
(Funding acquisition, Resources)
2
Institute of Applied Physics of the Russian Academy of Sciences
, Nizhny Novgorod 603950,
Russia
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Yang Yan
Yang Yan
(Funding acquisition, Supervision)
1
Terahertz Science and Technology Key Laboratory of Sichuan Province, School of Electronic Science and Engineering, University of Electronic Science and Technology of China
, Chengdu 610054,
China
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a)Author to whom correspondence should be addressed: fuwenjie@uestc.edu.cn
Phys. Plasmas 29, 093107 (2022)
Article history
Received:
July 16 2022
Accepted:
August 22 2022
Citation
Dun Lu, Wenjie Fu, Alexey Fedotov, Mikhail Glyavin, Mikhail Proyavin, Yang Yan; Ultimate transverse power of pulsed low-voltage gyrotron beam. Phys. Plasmas 1 September 2022; 29 (9): 093107. https://doi.org/10.1063/5.0110498
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