双共焦波导结构二次谐波太赫兹回旋管谐振腔设计  

Design of second harmonic terahertz gyrotron cavity based on double confocal waveguide

作　　者：关晓通 傅文杰[2] 鲁钝 杨同斌 鄢扬[2] 袁学松[2] Guan Xiao-Tong;Fu Wen-Jie;Lu Dun;Yang Tong-Bin;Yan Yang;Yuan Xue-Song(School of Physics,University of Electronic Science and Technology of China,Chengdu 610054,China;Terahertz Research Center,School of Electronic Science and Engineering,University of Electronic Science and Technology of China,Chengdu 610054,China)

机构地区：[1]电子科技大学物理学院,成都610054 [2]电子科技大学电子科学与工程学院,太赫兹研究中心,成都610054

出　　处：《物理学报》2020年第6期228-237,共10页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2019YFA210202);国家自然科学基金(批准号:61971097,61771096);中央高校基本科研业务费(批准号:ZYGX2019J012);太赫兹科学技术四川省重点实验室基金项目(批准号:THZSC201801)资助的课题~~

摘　　要：准光共焦波导具有功率容量大、模式密度低的特点,能够有效地减少模式竞争对回旋管互作用的影响,有利于高次谐波太赫兹回旋管的设计.为提高太赫兹准光回旋管的互作用效率,在共焦柱面波导的基础上,研究了一种新型高频互作用结构——双共焦波导结构,设计了一种330 GHz二次谐波双共焦结构回旋管谐振腔并对其进行了理论分析和粒子模拟.研究结果表明,双共焦谐振腔中的高阶模式能够与高次电子回旋谐波发生稳定的相互作用,并且没有模式竞争现象,具备工作在太赫兹波段的潜力.相比普通共焦波导谐振腔,双共焦谐振腔能够增强准光回旋管的注波互作用强度,提高回旋管的输出功率和工作效率.此外,结果还表明双共焦波导中的电磁波模式是一种由两个独立的共焦波导模式叠加而成的混合模式.利用这种混合模式有望实现太赫兹回旋管的单注双频工作,为新型太赫兹辐射源的研究提供了新的途径.Quasi-optical confocal cylindrical waveguide possesses a lot of good characteristics,such as big power capacity and low mode density,which can suppress the mode competition in beam-wave interaction.So quasioptical waveguide has a great advantage in designing high harmonic terahertz gyrotrons.For the reason that part of electron beams located in a region of weak field intensity play a limited role in beam-wave interactions,the beam-wave interaction is not efficient in confocal cavity.Motivated by enhancing the beam-wave interaction efficiency of quasi-optical gyrotron,we propose a novel terahertz harmonic gyrotron cavity with double confocal waveguide in this paper.The transverse field distribution and the mode spectrum in double confocal waveguide are analyzed and presented.A 330 GHz second harmonic gyrotron with double confocal cavity is designed,theoretically analyzed and simulated by using a particle-in-cell(PIC)code.The results obtained for double confocal cavity are compared with the results for single confocal cavity,and the physical mechanism of beamwave interaction enhancement in double confocal cavity is discussed.Theoretical results show that the double confocal cavity is able to increase the coupling strength of beam-wave interaction,thus,to improve the output power and the interaction efficiency of quasi-optical gyrotron.The PIC simulation results suggest that a highorder waveguide mode in double confocal cavity can steadily interact with the high harmonic cyclotron mode of electron beam without mode competition.Driven by a 40 kV,2 A electron beam with a guiding center radius of 1.65 mm and velocity ratio equal to 1.5,output power of 9.9 kW at 328.93 GHz can be generated in the designed double confocal cavity.The beam-wave interaction efficiency increases from 5.3%in single confocal cavity to 12.4%in dual confocal cavity under the same operation parameters.The double confocal cavity has great potential applications in terahertz band.Moreover,this study indicates that the eigen mode in double confocal

关 键 词：太赫兹回旋管 二次谐波 准光谐振腔 双共焦波导 

分 类 号：TN12[电子电信—物理电子学]