Open AccessInvestigation of an X band high efficiency klystron-like relativistic backward wave oscillator
Author(s) -
Dewen Yang,
Changhua Chen,
Yanchao Shi,
Renzhen Xiao,
Yuping Teng,
Zhiqiang Fan,
Wenyuan Liu,
Zhimin Song,
Jing Sun
Publication year - 2020
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.69.20200434
Subject(s) - klystron , physics , energy conversion efficiency , optics , electric field , cathode ray , electron , x band , reflector (photography) , modulation (music) , magnetic field , atomic physics , beam (structure) , optoelectronics , nuclear physics , quantum mechanics , acoustics , light source
This paper investigates an X band high efficiency klystron-like relativistic backward wave oscillator (RBWO) in detail. The klystron-like RBWO consists of a pre-modulation cavity, a resonant reflector with a ridge, a sectional slow wave structure, and an extraction cavity. First, this paper gives some theoretical studies about beam modulation and energy extraction. For beam modulation, the optimized distance between the pre-modulation cavity and the resonant reflector is studied theoretically, and theoretical results agree well with simulation results. For energy extraction, an ellipse extraction cavity with high power capacity is come up with, and the electric field on the inner surface of the ellipse extraction cavity decreases by 25% in PIC simulation. Also, the paper analyzes the effect of the position of dumped electron on conversion efficiency. Interestingly, it’s found that the efficiency dramatically decreases with the increase of the distance between the extraction cavity and the position of dumped electron, which is caused by the increase of potential energy of electron and the decrease of electric field. Fortunately, we find that the use of guiding magnet with special magnetic field distribution almost eliminate this unfavorable effect. Besides, effects of the distance between the cathode and anode L ak are investigated. It’s shown that the optimized diode voltage decrease with the increase of the distance L ak , and the conversion efficiency is higher at larger L ak . The experimental studies are also given. The power capacity of ellipse extraction cavity is verified, also we find that the efficiency is enhanced by 10% and the width of microwave pulse increases by 7 ns when the roughness of RF structure surface is improved from Ra 0.4 μm to Ra 0.05 μm. Typically, the klystron-like RBWO outputs X band high power microwave with power of 2.15 GW, with pulse duration of 25 ns, and with conversion efficiency of 50%(± 5%). Experimental results agree well with theoretical and PIC simulation results.