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Explosive emission cathode (EEC) is a pivotal component in high power microwave source (HPMS), of which the ultimate properties are significantly dependent on the quality of electron beams generated from the cathode. Short lifetime and poor emission uniformity are the persistent drawbacks of conventional field EEC. Improvement of cathode material by changing its compositions and modifying surface micromorphology, is a feasible way to solve this problem. Graphite is one of the frequently used materials for EECs due to its long life-time and sturdy performance under high voltage and repetition frequency. Meanwhile silicon carbide (SiC) whiskers are distinguished by high aspect ratio (ratio of height to diameter) and low work function which is in favor of the fast onset of electron emission. In this work, the novel composites, composed of SiC whiskers, pitch and major graphite powders, are prepared by the conventional mingling and sintering. The cathodes are installed on TPG1000 system with a parameterized pulse of 970 kV, 9.2 kA, and 50 ns. By analyzing the changes of the rise edge of measured diode current and output microwave pulse duration, the effects of material composition and surface micromorphology on electron emission properties for the cathode are disclosed in detail. The results, based on the comparison of emission properties between graphite cathodes with and without SiC whiskers doped, reveal that SiC whiskers play an important role in accelerating the field emission of cathode, which is demonstrated by the eclipse of displacement current peak on the rise edge of measured current waveform after doping. Meanwhile, the duration of output microwave pulse is enhanced by about 11% after doping, which could be explained by the lower expansion speed of Si plasma. Moreover, the surface micro-protrusions of graphite cathode doped by SiC whiskers are constantly “polished” by heating effect and cathode plasma as the number of emission pulses increases to 11000. This is in quite good agreement with the appearance of the displacement current peak on the rise edge of measured current curves after 6000 and 11000 pulses treatment. These changes imply that the initial speed of field emission from cathode is slowed down gradually. The output microwave pulse starts early, which is benefited from the homogeneous surface micromorphology of the cathode due to “polishing” effect. The quantity of releasing absorbed gases, including water and vacuum pump oil vapor, decreases with increasing emission pulses. Then the pulse shortening phenomenon is restrained and the falling edge of output microwave pulse is extended. The duration of output microwave pulse is increased by about 5%, for graphite cathode doped by SiC whiskers after experiencing 11000 pulses. In conclusion, the reaction mechanism of SiC whiskers in the process of explosive electron emission (EEE) is considered as being due to accelerating the onset of felid emission and reducing the expansion speed of cathode plasma. Therefore, combination with SiC whiskers is an effective way to improve the electron emission properties of graphite EECs, especially in the output microwave pulse width and energy conversion efficiency of HPMS.
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Keywords:
- surface microstructure /
- silicon carbide whisker /
- electron emission property /
- microwave pulse duration
[1] Benford J, Swegl J A, Schamiloglu E (translated by Jiang W H, Zhang C) 2009 High Power Microwaves (2nd Ed.) (Beijing: National Defense Industry Press) p35 (in Chinese) [本福德J, 斯威格J A, 谢米洛格鲁E 著（江伟华，张驰 译) 2009 高功率微波 (第二版) (北京：国防工业出版社) 第35页]
[2] Sun J 2006 Ph. D. Dissertation (Beijing: Tsinghua University) (in Chinese) [孙钧 2006 博士学位论文(北京: 清华大学)]
[3] Zhang Y H, Song F L, Xiang F, Kang Q, Luo M, Gong S G 2008 High Power Laser Particle Beams 20 863 (in Chinese) [张永辉, 宋法伦, 向飞，康强，罗敏，龚胜刚 2008 强激光与粒子束 20 863]
[4] Jin Z X, Zhang J, Lei Y, Qian B L, Fan Y W, Zhou S Y 2011 High Power Laser Particle Beams 23 1307 (in Chinese) [靳振兴, 张军, 雷应，钱宝良，樊玉伟，周生岳 2011 强激光与粒子束 23 1307]
[5] Krasik Y E, Dunaevsky A, Gleizer J Z, Felsteiner J, Kotov Y A, Sokovnin S Y, Balezin M E 2002 J. Appl. Phys. 91 9385
[6] Bykov N M, Gubanov V P, Gunin A V, Ksrovin S D, Kutenkov O P, Landl V F, Polevin S D, Rostov V V, Mesyats G A, Zagulov F Y 1995 Proceeding of the 10th IEEE International Pulsed Power Conference Albuquerque, NM, USA, July 3-6, 1995 p71
[7] Gunin A V, Landl V F, Korovin S D, Mesyats G A, Pegel I V, Rostov V V 2000 IEEE Trans. Plasma Sci. 28 537
[8] Korovin S D, Rostov V V, Polevin S D 2004 Proc. IEEE 92 1082
[9] Shiffler D, Ruebush M, Zagar D, LaCour M, Golby K 2002 IEEE Trans. Plasma Sci. 91 1592
[10] Roy A, Patel A, Menon R, Sharma A, Chakravarthy D P, Patil D S 2011 Phys. Plasmas 18 103108
[11] Shiffler D, Ruebush M, Zagar D, LaCour M, Golby K, Umstattd R, Clark M C 2001 Appl. Phys. Lett. 79 2871
[12] Russell C R 1967 Elements of Energy Conversion (London: Pergamon Press) p305
[13] Qin Y X, Hu M 2008 Appl. Surf. Sci. 254 3315
[14] Puchkarev V F, Mesyats G A 1995 J. Appl. Phys. 78 5633
[15] Sun J, Wu P, Huo S F, Tan W B, Shao H, Chen C H, Liu G Z 2014 IEEE Trans. Plasma Sci. 42 2179
[16] Huo S F 2011 M. S. Thesis (Xi’an: Northwest Institute of Nuclear Technology) (in Chinese) [霍少飞 2011 硕士学位论文 (西安: 西北核技术研究所)]
[17] Wu P, Huo S F, Sun J, Chen C H, Liu G Z 2015 Phys. Plasmas 22 083104
[18] Wu P, Sun J, Ye H 2015 Phys. Plasmas 22 063109
[19] McBride R D, Jennings C A, Vesey R A, Rochau GＡ, Savage M E, Stygar W A, Cuneo M E, Sinars D B, Jones M, LeChien K R, Lopez M R, Moore J K, Struve K W, Wagoner T C, Waisman E M 2010 Phys. Rev. Spec. Top. Accel Beams 13 120401
[20] Gong Y B, Zhang Z, Wei Y Y, Meng F B, Fan Z K, Wang W X 2004 Acta Phys. Sin. 53 3990 (in Chinese) [宫玉彬, 张章, 魏彦玉，孟凡宝，范植开，王文祥 2004 物理学报 53 3990]
[21] Benford J, Benford G 1997 IEEE Trans. Plasma Sci. 5 2
[22] Goebel D M 1998 IEEE Trans. Plasma Sci. 26 3
[23] Fursey G N, Polyakov M A, Shirochin L A, Saveliev A N 2003 Appl. Surf. Sci. 215 286
[24] Korovin S D, Litvinov E A, Mesyats G A, Rostov V V, Rukin S N, Shpak V G, Yalandin M I 2006 IEEE Trans. Plasma Sci. 34 1771
[25] Mesyats G A (translated by Li G Z) 2007 Vacuum Discharge Physics and High Power Pulse Technology (Beijing: National Denfense Industry Press) pp297-298 (in Chinese) [米夏兹G A 著 (李国政 译) 2007 真空放电物理和高功率脉冲技术 (北京: 国防工业出版社) 第297-298页]
[26] Mesyats G A, Zubarev N M 2015 J. Appl. Phys. 117 043302
[27] Mesyats G A 1995 IEEE Trans. Plasma Sci. 23 879
[28] Barengolts S A, Mesyats G A, Shmelev D L 2003 IEEE Trans. Plasma Sci. 31 809
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[1] Benford J, Swegl J A, Schamiloglu E (translated by Jiang W H, Zhang C) 2009 High Power Microwaves (2nd Ed.) (Beijing: National Defense Industry Press) p35 (in Chinese) [本福德J, 斯威格J A, 谢米洛格鲁E 著（江伟华，张驰 译) 2009 高功率微波 (第二版) (北京：国防工业出版社) 第35页]
[2] Sun J 2006 Ph. D. Dissertation (Beijing: Tsinghua University) (in Chinese) [孙钧 2006 博士学位论文(北京: 清华大学)]
[3] Zhang Y H, Song F L, Xiang F, Kang Q, Luo M, Gong S G 2008 High Power Laser Particle Beams 20 863 (in Chinese) [张永辉, 宋法伦, 向飞，康强，罗敏，龚胜刚 2008 强激光与粒子束 20 863]
[4] Jin Z X, Zhang J, Lei Y, Qian B L, Fan Y W, Zhou S Y 2011 High Power Laser Particle Beams 23 1307 (in Chinese) [靳振兴, 张军, 雷应，钱宝良，樊玉伟，周生岳 2011 强激光与粒子束 23 1307]
[5] Krasik Y E, Dunaevsky A, Gleizer J Z, Felsteiner J, Kotov Y A, Sokovnin S Y, Balezin M E 2002 J. Appl. Phys. 91 9385
[6] Bykov N M, Gubanov V P, Gunin A V, Ksrovin S D, Kutenkov O P, Landl V F, Polevin S D, Rostov V V, Mesyats G A, Zagulov F Y 1995 Proceeding of the 10th IEEE International Pulsed Power Conference Albuquerque, NM, USA, July 3-6, 1995 p71
[7] Gunin A V, Landl V F, Korovin S D, Mesyats G A, Pegel I V, Rostov V V 2000 IEEE Trans. Plasma Sci. 28 537
[8] Korovin S D, Rostov V V, Polevin S D 2004 Proc. IEEE 92 1082
[9] Shiffler D, Ruebush M, Zagar D, LaCour M, Golby K 2002 IEEE Trans. Plasma Sci. 91 1592
[10] Roy A, Patel A, Menon R, Sharma A, Chakravarthy D P, Patil D S 2011 Phys. Plasmas 18 103108
[11] Shiffler D, Ruebush M, Zagar D, LaCour M, Golby K, Umstattd R, Clark M C 2001 Appl. Phys. Lett. 79 2871
[12] Russell C R 1967 Elements of Energy Conversion (London: Pergamon Press) p305
[13] Qin Y X, Hu M 2008 Appl. Surf. Sci. 254 3315
[14] Puchkarev V F, Mesyats G A 1995 J. Appl. Phys. 78 5633
[15] Sun J, Wu P, Huo S F, Tan W B, Shao H, Chen C H, Liu G Z 2014 IEEE Trans. Plasma Sci. 42 2179
[16] Huo S F 2011 M. S. Thesis (Xi’an: Northwest Institute of Nuclear Technology) (in Chinese) [霍少飞 2011 硕士学位论文 (西安: 西北核技术研究所)]
[17] Wu P, Huo S F, Sun J, Chen C H, Liu G Z 2015 Phys. Plasmas 22 083104
[18] Wu P, Sun J, Ye H 2015 Phys. Plasmas 22 063109
[19] McBride R D, Jennings C A, Vesey R A, Rochau GＡ, Savage M E, Stygar W A, Cuneo M E, Sinars D B, Jones M, LeChien K R, Lopez M R, Moore J K, Struve K W, Wagoner T C, Waisman E M 2010 Phys. Rev. Spec. Top. Accel Beams 13 120401
[20] Gong Y B, Zhang Z, Wei Y Y, Meng F B, Fan Z K, Wang W X 2004 Acta Phys. Sin. 53 3990 (in Chinese) [宫玉彬, 张章, 魏彦玉，孟凡宝，范植开，王文祥 2004 物理学报 53 3990]
[21] Benford J, Benford G 1997 IEEE Trans. Plasma Sci. 5 2
[22] Goebel D M 1998 IEEE Trans. Plasma Sci. 26 3
[23] Fursey G N, Polyakov M A, Shirochin L A, Saveliev A N 2003 Appl. Surf. Sci. 215 286
[24] Korovin S D, Litvinov E A, Mesyats G A, Rostov V V, Rukin S N, Shpak V G, Yalandin M I 2006 IEEE Trans. Plasma Sci. 34 1771
[25] Mesyats G A (translated by Li G Z) 2007 Vacuum Discharge Physics and High Power Pulse Technology (Beijing: National Denfense Industry Press) pp297-298 (in Chinese) [米夏兹G A 著 (李国政 译) 2007 真空放电物理和高功率脉冲技术 (北京: 国防工业出版社) 第297-298页]
[26] Mesyats G A, Zubarev N M 2015 J. Appl. Phys. 117 043302
[27] Mesyats G A 1995 IEEE Trans. Plasma Sci. 23 879
[28] Barengolts S A, Mesyats G A, Shmelev D L 2003 IEEE Trans. Plasma Sci. 31 809
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