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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 Lak are investigated. It’s shown that the optimized diode voltage decrease with the increase of the distance Lak, and the conversion efficiency is higher at larger Lak. 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.
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Keywords:
- high efficiency /
- klystron-like /
- relativistic backward wave oscillator /
- high power microwave
[1] Nation 1970 J Appl. Phys. Lett. 17 491
Google Scholar
[2] Kovalev N F, Petelin M I, Raizer M D, Smorgonskii A V, Tsopp L E 1973 JETP Lett. 18 138
[3] Bromborsky A, Still G W, Kehs R A, Clark C, Early L, Rohwein G, Poukey J 1989 J. Appl. Phys. 66 3871
Google Scholar
[4] Chen C H, Liu G Z, Huang W H, Song Z M, Fan J P, Wang H J 2002 IEEE Trans. Plasma Sci. 30 1108
Google Scholar
[5] Xiao R Z, Chen C H, Zhang X W, Sun J 2009 J. Appl. Phys. 105 053306
Google Scholar
[6] Xiao R Z, Zhang X W, Zhang L J, Li X Z, Zhang L G, Song W, Hu Y M, Sun J, Huo S F, Chen C H, Zhang Q Y, Liu G Z 2010 Laser Part. Beams 28 505
Google Scholar
[7] Tot’meninov E M, Vykhodtsev P V, Kitsanov S A, Klimov A I, Rostov V V 2011 Technical Physics 56 1009
Google Scholar
[8] Jin Z X, Zhang J, Yang J H, Zhong H H, Qian B L, Shu T, Zhang J D, Zhou S Y, Xu L R 2011 Rev. Sci. Instrum. 82 084704
Google Scholar
[9] Wu P, Fan J P, Teng Y, Shi Y C, Deng Y Q, S un 2014 J Phys. Plasmas 21 103110
Google Scholar
[10] Yang D W, Shi Y C, Xiao R Z, Teng Y, Sun J, Chen C H 2018 AIP Advances 8 095229
Google Scholar
[11] Korovin S D, Polevin S D, Roitman A M, Rostov V V 1996 Russian Physics Journal 39 1206
Google Scholar
[12] Yang D W, Chen C H, Xiao R Z, Shi Y C, Cao Y B, Teng Y, Sun J 2018 Phys. Plasmas 25 123101
Google Scholar
[13] Xiao R Z, Chen C H, Cao Y B, Sun J 2013 J. Appl. Phys. 114 213301
Google Scholar
[14] Rostov V V, Gunin A V, Tsygankov R V, Romanchenko I V, Yalandin M I 2018 IEEE Trans. Plasma Sci. 46 33
Google Scholar
[15] Rostov V V, Totmeninov E M, Tsygankov R V, Kurkan I K, Kovalchuk O B, Elchaninov A A, Stepchenko A S, Gunin A V, Konev V Y, Yushchenko A Y, Emelyanov E V 2018 IEEE Transactions on Electron Devices 65 3019
Google Scholar
[16] 史彦超, 陈昌华, 肖仁珍, 滕雁, 邓昱群, 孙钧 2015 第十届全国高功率微波学术研讨会, 呼和浩特, 2015
Shi Y C, Chen C H, Xiao R Z, Teng Y, Deng Y Q, Sun J 2015 The Tenth High Power Microwave Conference, Huhehot (in Chinese)
[17] 郭硕鸿 2008 电动力学 (第3版） (北京: 高等教育出版社)
Guo S H 2008 Electrodynamics (3rd Ed.) (Beijing: Higher Education Press) (in Chinese)
[18] Xiao R Z, Chen C H, Sun J, Zhang X W, Zhang L J 2011 Appl. Phys. Lett. 98 101502
Google Scholar
[19] Swegle J A, Poukey J W, Leifeste G T 1985 Physics of Fluids 28 2882
Google Scholar
[20] Cao Y B, Sun J, Zhang Y C, Song Z M, Wu P, Fan Z Q, Teng Y, He T, Chen C H 2018 IEEE Trans. Plasma Sci. 46 90
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图 1 一种高效率速调型相对论返波管结构图 (1 预调制腔; 2调制脊; 3 慢波结构; 4 提取腔; 5 电子束收集极; 6谐振腔反射器; 7电子束; 8 引导磁体; 9 阴极)
Figure 1. Schematic of a high efficiency klystron-like RBWO. (1 pre-modulation cavity; 2 modulation ridge; 3 slow wave structure; 4 extraction cavity; 5 electron beam collector; 6 resonant reflector; 7 electron beam; 8 guiding magnet; 9 cathode)
图 2 含两个预调制腔的预调制结构
Figure 2. Pre-modulation structure with two cavities.
图 3 两个调制腔间距L1对效率的影响
Figure 3. Effect of the two modulation cavity spacing L1 on efficiency.
图 4 提取腔改进的示意图 (a)矩形提取腔; (b)“理想”提取腔
Figure 4. Schematic of enhanced extraction cavity: (a) Rectangular extraction cavity; (b) perfect extraction cavity.
图 5 两种提取腔结构示意图 (a)矩形提取腔; (b)椭圆形提取腔
Figure 5. Schematic of two extraction cavities: (a) Rectangular extraction cavity; (b) ellipse extraction cavity.
图 6 PIC仿真中矩形提取腔中的场强分布 (a)电场分量Ez朝–z方向的情形; (b)电场分量Ez朝+z方向的情形
Figure 6. Field distribution in rectangular extraction cavity in PIC simulation: (a) Ez orients –z direction; (b) Ez orients +z direction.
图 7 PIC仿真中椭圆形提取腔中的纵向电场分布 (a)纵向电场Ez朝–z方向的情形; (b)纵向电场Ez朝+z方向的情形
Figure 7. Longitudinal electric field distribution in ellipse extraction cavity in PIC simulation: (a) Ez orients –z direction; (b) Ez orients +z direction.
图 8 超导磁体的磁场
Figure 8. Magnetic field of superconductor magnet.
图 9 螺线管磁场和超导磁场下的相空间图 (a)螺线管磁体的情形; (b)超导磁场的情形
Figure 9. Phasespace of electron beam under solenoid and superconductor magnet: (a) Case with solenoid magnet; (b) case with superconductor magnet.
图 10 螺线管磁场和超导磁场下的效率随Lec的变化
Figure 10. Variation of efficiency with Lec under solenoid and superconductor magnet.
图 11 PIC数值模拟中的典型结果 (a)输出功率; (b)频谱
Figure 11. Typical results in PIC simulation: (a) Microwave power; (b) frequency spectrum.
图 12 不同阴阳极间距Lak的电压规律 (a)效率随电压的变化; (b)频率随电压的变化
Figure 12. Effect of diode voltage under different Lak: (a) Variation of efficiency with diode voltage; (b) variation of frequency with diode voltage.
图 13 实验系统示意图
Figure 13. Schematic of experiment system.
图 14 速调型相对论返波管外观
Figure 14. Picture of the Klystron-like RBWO.
图 15 辐射场测量系统示意图
Figure 15. Schematic of measurement system.
图 16 检波器的标定曲线
Figure 16. Calibration result of envelope detector.
图 17 不同粗糙度的表面 (a)粗糙度Ra = 0.4; (b)粗糙度Ra = 0.05
Figure 17. Surface with different roughness: (a) Roughness Ra = 0.4; (b) roughness Ra = 0.05.
图 18 不同粗糙度时的输出波形 (a)粗糙度Ra = 0.4; (b)粗糙度Ra = 0.05. (通道1: 在线微波波形; 通道2, 3: 辐射场微波波形)
Figure 18. Output waveform for different roughness: (a) Roughness Ra = 0.4; (b) Roughness Ra = 0.05. (channel 1, online microwave; channel 2 and 3, radiation field)
图 19 不同粗糙度120个微波脉冲后的表面痕迹 (a)粗糙度Ra = 0.4; (b)粗糙度Ra = 0.05
Figure 19. Breakdown traces after 120 pulses for different roughness: (a) Roughness Ra = 0.4; (b) roughness Ra = 0.05.
图 20 提取腔的寿命现象 (a) 100个脉冲后; (b) 130个脉冲后. (通道1: 在线微波波形; 通道2, 3: 辐射场微波波形)
Figure 20. Lifetime of extraction cavity: (a) After 100 pulses; (b) after 130 pulses. (channel 1, online microwave; channel 2 and 3, radiation field)
图 21 矩形提取腔和椭圆形提取腔时的波形 (a)矩形提取腔; (b)椭圆形提取腔. (通道1: 二极管电压波形; 通道2: 二极管电流波形; 3: 辐射场波形)
Figure 21. Waveform under rectangular and ellipse extraction cavity: (a) Rectangular extraction cavity; (b) ellipse extraction cavity. (channel 1, diode voltage; channel 2, diode current; channel 3, radiation field)
图 22 40个微波脉冲后的击穿痕迹 (a)矩形提取腔; (b)椭圆形提取腔
Figure 22. Breakdown trace after 40 pulses: (a) Rectangular extraction cavity; (b) ellipse extraction cavity.
图 23 辐射场功率密度分布
Figure 23. Power density distribution of radiation field.
图 24 微波波形和频谱
Figure 24. Microwave waveform and frequency spectrum.
表 1 矩形提取腔各参数
Table 1. Parameters of rectangular extraction cavity.
参数 rrec/mm Lrec/mm rrec1/mm rrec2/mm rc/mm 取值 31.00 7.00 2.25 2.00 23.00 
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表 2 椭圆形提取腔各参数
Table 2. Parameters of ellipse extraction cavity.
参数 R0/mm Z0/mm rec/mm zec/mm r1/mm r2/mm Le/mm rc/mm 取值 8.50 2.25 32.00 243.00 0.75 4.00 6.75 23.00
DownLoad: CSV
表 3 测量元件的衰减标定值
Table 3. Calibration result of measurement element.
部件 衰减值/dB 衰减器 26.256 5 m微波缆 5.165 定向耦合器和波同转换器 30.05
DownLoad: CSV
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[1] Nation 1970 J Appl. Phys. Lett. 17 491
Google Scholar
[2] Kovalev N F, Petelin M I, Raizer M D, Smorgonskii A V, Tsopp L E 1973 JETP Lett. 18 138
[3] Bromborsky A, Still G W, Kehs R A, Clark C, Early L, Rohwein G, Poukey J 1989 J. Appl. Phys. 66 3871
Google Scholar
[4] Chen C H, Liu G Z, Huang W H, Song Z M, Fan J P, Wang H J 2002 IEEE Trans. Plasma Sci. 30 1108
Google Scholar
[5] Xiao R Z, Chen C H, Zhang X W, Sun J 2009 J. Appl. Phys. 105 053306
Google Scholar
[6] Xiao R Z, Zhang X W, Zhang L J, Li X Z, Zhang L G, Song W, Hu Y M, Sun J, Huo S F, Chen C H, Zhang Q Y, Liu G Z 2010 Laser Part. Beams 28 505
Google Scholar
[7] Tot’meninov E M, Vykhodtsev P V, Kitsanov S A, Klimov A I, Rostov V V 2011 Technical Physics 56 1009
Google Scholar
[8] Jin Z X, Zhang J, Yang J H, Zhong H H, Qian B L, Shu T, Zhang J D, Zhou S Y, Xu L R 2011 Rev. Sci. Instrum. 82 084704
Google Scholar
[9] Wu P, Fan J P, Teng Y, Shi Y C, Deng Y Q, S un 2014 J Phys. Plasmas 21 103110
Google Scholar
[10] Yang D W, Shi Y C, Xiao R Z, Teng Y, Sun J, Chen C H 2018 AIP Advances 8 095229
Google Scholar
[11] Korovin S D, Polevin S D, Roitman A M, Rostov V V 1996 Russian Physics Journal 39 1206
Google Scholar
[12] Yang D W, Chen C H, Xiao R Z, Shi Y C, Cao Y B, Teng Y, Sun J 2018 Phys. Plasmas 25 123101
Google Scholar
[13] Xiao R Z, Chen C H, Cao Y B, Sun J 2013 J. Appl. Phys. 114 213301
Google Scholar
[14] Rostov V V, Gunin A V, Tsygankov R V, Romanchenko I V, Yalandin M I 2018 IEEE Trans. Plasma Sci. 46 33
Google Scholar
[15] Rostov V V, Totmeninov E M, Tsygankov R V, Kurkan I K, Kovalchuk O B, Elchaninov A A, Stepchenko A S, Gunin A V, Konev V Y, Yushchenko A Y, Emelyanov E V 2018 IEEE Transactions on Electron Devices 65 3019
Google Scholar
[16] 史彦超, 陈昌华, 肖仁珍, 滕雁, 邓昱群, 孙钧 2015 第十届全国高功率微波学术研讨会, 呼和浩特, 2015
Shi Y C, Chen C H, Xiao R Z, Teng Y, Deng Y Q, Sun J 2015 The Tenth High Power Microwave Conference, Huhehot (in Chinese)
[17] 郭硕鸿 2008 电动力学 (第3版） (北京: 高等教育出版社)
Guo S H 2008 Electrodynamics (3rd Ed.) (Beijing: Higher Education Press) (in Chinese)
[18] Xiao R Z, Chen C H, Sun J, Zhang X W, Zhang L J 2011 Appl. Phys. Lett. 98 101502
Google Scholar
[19] Swegle J A, Poukey J W, Leifeste G T 1985 Physics of Fluids 28 2882
Google Scholar
[20] Cao Y B, Sun J, Zhang Y C, Song Z M, Wu P, Fan Z Q, Teng Y, He T, Chen C H 2018 IEEE Trans. Plasma Sci. 46 90
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