真空表面绝缘特性研究
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摘要
绝缘子的真空表面绝缘特性研究真空下的高压沿绝缘子表面击穿物理过程，称真空表面闪络过程。影响该过程的因素包括绝缘材料结构、空间电场分布、表面处理方法、所加电压特征，脉冲宽度等。研究真空表面闪络过程有两类理论：二次电子发射崩溃(SEEA)和电子引发极化松弛(ETPR)。SEEA理论以绝缘子表面在电子轰击下发射二次电子为基础，包含了电子诱发脱附(ESD)，和脱附气体离子化并对闪络过程产生影响等过程，对表面闪络现象进行了解释。
本文分析了二次电子发射过程的经验公式，推导了真空表面闪络的稳定条件，以SEEA理论的观点描述了真空表面闪络发生的物理图象。对影响表面闪络发生因素，提高表面闪络电压阈值方法进行了分析。
在长脉冲加速器上(500kV，3kA，1μs)进行了表面闪络现象的观测研究工作。使用KARAT程序分析了无箔二极管的回流屏蔽方法，实验中发现加屏蔽环后表面闪络电压从300kV提高到了400kV。发现外加6000高斯磁场后，表面闪络电压降低～20％。对绝缘子损伤后的绝缘子表观结构也进行了观察。
总结提出了绝缘子设计的三点基本考虑：
1、选择真空性能好的绝缘子，减少可能存在的弱点；
2、尽量降低三结合点电场强度；
3、使电场沿绝缘子表面分布尽量均匀。
设计出工作于脉宽200ns脉冲电压下的最高电压750kV锥形绝缘子，并进行了结构优化。锥形绝缘子高15cm，锥底直径35cm，锥顶直径5cm，实验结果表明满足设计要求，在600kV以上工作300多次，最高电压达750kV，运行稳定，未发生沿表面闪络现象。
The insulation characteristic of insulator in vacuum is researched in the process of the high voltage breakdown along the insulator surface in vacuum, which is called vacuum surface flashover. The factors which influenced the process include the insulator's material, structure, the distribution of space electrical field, the way to deal with the surface, the characteristic of voltage waveform, pulse width etc. There are two kinds of theory for the vacuum surface flashover: secondary electron emission avalanche (SEEA) and electron triggered polarization relaxation (ETPR). The theory of SEEA is based on the insulator's surface emitted secondary electrons when bombarded by electron, includes the process of electron-simulated desorption (ESD), the process of desorption gas ionization and the process of the ion influencing the flashover.
The empirical formula in the process of the secondary emission is analyzed; the stabilization condition of vacuum surface flashover is deduced. The physics image of the vacuum surface flashover is described with the SEEA theory. The factors which influenced the surface flashover and the way to rise the withstand voltage are also been analyzed.
The observation and research are done on the long pulse accelerator (500kV, 3kA, 1μs). The way to shield the back current of foilless diode is analyzed by KARAT program. The surface flashover is raised from 300kV to 400kV when the shield is added in experiments. And the surface flashover decreased about 20% when a magnetic field of about 6000 gauss added. The surface structure of the damaged insulator by flashover is also observed.
Summarized three consideration in the design of insulator.
1. choose the good vacuum characteristic insulator, reduce the probable weakness;
2. reduce the electrical field in the triple junction as possible
3. make the electrical field distributing along the surface more uniform.
A conical insulator is designed, which is operated on the maximum voltage 750kV and pulse width 200ns. The conical insulator high 15 cm,the diameter of top is 5cm and that of the bottom is 35cm. The insulator is operated for more 300 times on voltage more 600kV, and maximum voltage is 750kV. The operated is stability and no surface flashover phenomenon is happened.
本文分析了二次电子发射过程的经验公式，推导了真空表面闪络的稳定条件，以SEEA理论的观点描述了真空表面闪络发生的物理图象。对影响表面闪络发生因素，提高表面闪络电压阈值方法进行了分析。
在长脉冲加速器上(500kV，3kA，1μs)进行了表面闪络现象的观测研究工作。使用KARAT程序分析了无箔二极管的回流屏蔽方法，实验中发现加屏蔽环后表面闪络电压从300kV提高到了400kV。发现外加6000高斯磁场后，表面闪络电压降低～20％。对绝缘子损伤后的绝缘子表观结构也进行了观察。
总结提出了绝缘子设计的三点基本考虑：
1、选择真空性能好的绝缘子，减少可能存在的弱点；
2、尽量降低三结合点电场强度；
3、使电场沿绝缘子表面分布尽量均匀。
设计出工作于脉宽200ns脉冲电压下的最高电压750kV锥形绝缘子，并进行了结构优化。锥形绝缘子高15cm，锥底直径35cm，锥顶直径5cm，实验结果表明满足设计要求，在600kV以上工作300多次，最高电压达750kV，运行稳定，未发生沿表面闪络现象。
The insulation characteristic of insulator in vacuum is researched in the process of the high voltage breakdown along the insulator surface in vacuum, which is called vacuum surface flashover. The factors which influenced the process include the insulator's material, structure, the distribution of space electrical field, the way to deal with the surface, the characteristic of voltage waveform, pulse width etc. There are two kinds of theory for the vacuum surface flashover: secondary electron emission avalanche (SEEA) and electron triggered polarization relaxation (ETPR). The theory of SEEA is based on the insulator's surface emitted secondary electrons when bombarded by electron, includes the process of electron-simulated desorption (ESD), the process of desorption gas ionization and the process of the ion influencing the flashover.
The empirical formula in the process of the secondary emission is analyzed; the stabilization condition of vacuum surface flashover is deduced. The physics image of the vacuum surface flashover is described with the SEEA theory. The factors which influenced the surface flashover and the way to rise the withstand voltage are also been analyzed.
The observation and research are done on the long pulse accelerator (500kV, 3kA, 1μs). The way to shield the back current of foilless diode is analyzed by KARAT program. The surface flashover is raised from 300kV to 400kV when the shield is added in experiments. And the surface flashover decreased about 20% when a magnetic field of about 6000 gauss added. The surface structure of the damaged insulator by flashover is also observed.
Summarized three consideration in the design of insulator.
1. choose the good vacuum characteristic insulator, reduce the probable weakness;
2. reduce the electrical field in the triple junction as possible
3. make the electrical field distributing along the surface more uniform.
A conical insulator is designed, which is operated on the maximum voltage 750kV and pulse width 200ns. The conical insulator high 15 cm,the diameter of top is 5cm and that of the bottom is 35cm. The insulator is operated for more 300 times on voltage more 600kV, and maximum voltage is 750kV. The operated is stability and no surface flashover phenomenon is happened.
引文
[1] Wetzer J M., Wouters P A A F. HV design of vacuum components[J]. In: IEEE Trans. On Dielectrics and Electrical Insulation, 1995, 292): 202～209.
[2] Vlieks A E, Allen A, Callm R S. et al. Breakdown phenomena in high-power klystrons. IEEE Trans. On Electrical Insulation, 1989, 24(6): 1023～1028.
[3] Saito Y, Michizuo N, Anami S. et al. Surface flashover on alumina RF windows for high-power use. IEEE Trans. On Electrical Insulation, 1993, 24(4): 566～573.
[4] T. H. Martin et al. J. C. Martin on Pulse Power, New York, Plenum Press, 1996: 258.
[5] H. Craig Miller, Flashover of Insulators in Vacuum, IEEE Trans. Insul., 1993, Vol. 28: 512～527.
[6] S. E. Sampayan et al. Multilayer. High Gradient Insulator Technology,. IEEE Trans on Dielectrics and Electrical Insulation, Vol. 7(3): 334～339.
[7] 张冠军．真空中固体绝缘材料沿面闪络的起始机理与发展过程[D]．博士学位论文．西安：西安交通大学，2001．
[8] 丁立键，李成榕．真空中绝缘子的沿面闪络现象[J]．高电压技术，1999，25(2)：53～57．
[9] H. H. Zhong. Time characteristics of fast pulsed flashover in vacuum[J]. IEEE Trans on electrical insulation, 1992, vol.27(3): 496～503
[10] R. A. Anderson and J. P. Brainard. Mechanism of Pulsed Surface Flashover Involving Electron-stimulated Desorption [J-]. J. Appl. Phys., 1980, Vol. 51: 1414～1421.
[11] G. Blaise and C. Le Gressus, Charging and Flashover Induced by Surface Polarizetion Telaxation Process [J]. J. Appl. Phys., 1991, Vol. 69, 6334～6339.
[12] G. Blaise, New approach to flashover in dielectrics based on a polarization energy relaxation mechanism[J], IEEE trans. On Electrical Insulation, 1993, Vol. 28(4): 437～443
[13] P. A. Amold et al. 45degree insulator surface flashover a review and new results[A], VIIth. International Symposium on Discharges and Electrical Insulation in Vacuum: 231
[14] 孙大明，席光康，固体的表面与界面[M]，合肥，安徽教育出版社，1996
[15] E. A. Burke, Secondary emission from polymers[J], IEEE Trans on Nuclear Science, 1980, Vol. NS-27(6): 1760～1764.
[16] De Tourreil C H., Srivastave K D. Mechanusm of surface charging of high-voltage insulators in vacuum [J]. IEEE Trans. on electrical insulation, 1973, 8(1): 17-21.
[17] O. Yamamoto et al. Monte carlo simulation of surface charge on angled insulators in vacuum [J], IEEE Trans. on electrical insulation, 1993, vol. 28(4): 706～712.
[18] B H W Hendriks et al.. Modes in electron-hopping transport iver insulators sustained by secondary electron emission [J], J. phys. D: Appl. Phys. 30, 1997: 1252～1254.
[19] Ningsheng Xu et al.. Effects of geometry and polarity on the prebreakdown and flashover behavior of conical high-voltage insulators in vacuum [J], IEEE Trans. On plasma science, 1997, vol. 25(3): 447～454.
[20] Z. Nadolny, W. Ziomek. Field stress control for spacer in vacuum using varied geometry of triple junction [D], XVIIth international symposium on discharges and electrical insulation in vacuum, Berkeley, 1996: 527～531.
[21] G. Damamme, C. Le gressus, Simulation of the triple junction eggects in vacuum devices [D],1996 IEEE Annual Report-conference on electrical insulation and dielectric phenomena, San Franciscao, 1996: 562～566.
[22] T. S.Sudarshan, Electrode architecture related to surface flashover of solid dielectrics in vacuum[J],
IEEE trans, on dielectrics and electrical insulation, 1997, vol.4(4): 374～381.
[23] A. Sivathanu Pillai and Reuben Hackam. Influence of metal-insulator junction on surface flashover in vacuum [J-I, J. Appl. Phys. 1987, 61(11), 4992～4999
[24] I. D. Chalmers et al. Surface charging and flashover on insulators in vacuum [J], IEEE Trans. On dielectrics and electrical insulation, 1995, vol. 2(2): 225～230
[25] O. Yamamoto et al. Effects of spark conditioning, insulator angle and length on surface flashover in vacuum [j], IEEE Trans. Electrical insulation, 1989, vol. 24: 991～994
[26] A. S. Pillai and R. Hackam, Surface flashover of conical insulator in vacuum[J], J.appl.Phys,,1984,vol 56: 1374～1381
[27] A. Watson, Pulsed flashover in vacuum,[J], J.Appl. Phys., 1967, vol.38: 2019～2023
[28] O. Milton, Pulsed flashover of insulators in vacuum [J], IEEE Trans. Electrical insulation, 1972, vol. 7: 9～15
[29] J. Golen and C. A. Kapertanakos, Flashover breakdown of an insulator in vacuum by a voltage impulse in the presence of a magnetic field [J], J. Appl. Phys., 1977, vol. 48: 1756～1758.
[30] N. C. Jaitly and T. S. Sudarshan. Novel insulator designs for superior dc hold-off in bridhed vacuum gaps [J], IEEE Trans. electrical Insulation, 1987, vol. 22: 801～810.
[31] R. Lee et al. Predischarge current measurements in vacuum gaps bridged with pleciglas insulators[J], IEEE Trans. Electrical insulation., 1983, vol. 18: 280～286.
[32] Pillai A s, Hackam R. Surface flashover of solid dielectric in Vacuum [J], Journal of Applied Physics, 1982, 53(4): 2983～2987.
[33] Ian D. Smith, Flashover of vacuum interfaces with many stages and large transit times [J], IEEE Trans. On plasma science, 1997, vol. 25(2): 293～299.
[34] R. A. Anderson, Mechanism of fast surface flashover n vacuum[J], Appl. Ohys. Lett., 1974, vol.24: 54～56.
[35] R. Korzekwa et al., Inhibiting surface flashover of space conditions using magnetic fields [J], IEEE Trans. Plasma Sci., 1989,vol. 17: 612～615.
[36] J. P. Vandevender et al., magnetic inhibition of insulator flashover [J], J. appl. Phys., 1982, vol.53: 4441～4447
[37] Miller H C., Flashover of insulators in vacuum, reviews of the phenomena and techniques to improver holdoff voltage [J], IEEE Trans. On electrical insulation, 1993, 28(4): 512～527.
[38] Pillai A s, Hackam R. Surface flashover of solid insulators in atmospheric air and in vacuum[J]. Journal of applied physics, 1985, 58(1): 146～153.
[39] C. Le Gressus et al. Flashover in wide-band-gap high-purity insulators: methodology and mechanisms [J], J. appl. phys., 1991, vol. 69: 6325～6333
[40] S. Grzybowski et al., Electric surface strength and surface deterioration of thermoplastic insulators in vacuum[J], IEEE Trans. Electric insulation, 1983, vol. 18: 301～309.
[41] R. A. Anderson, Propagation velocity of cathode-initiated surface flashover [J], J. appl. phys., 1977, vol. 48: 4210～4214.
[42] J. D. Cross, High speed photography of surface flashover of dielectrics in a strong electric field [D], Proc. ⅩⅣ Int. Sym. Discharge electric insulation of Vacuum, Santafe, 1990, 365～367.
[43] J. E. Thompson et al., Investigations of fast insulator surface flashover in vacuum [J], IEEE Trans. Plasma Sci., 1980, vol. 8: 191～197.
[44] Tangal S. Sudarshan, The effect of chromium oxide coatings on surface flashover of alumina spacers in vacuum [J], IEEE Trans. On electrical insulation, 1976, vol. EI-11: 32～35.
[45] L. L. Hatfield et al. a treatment which improves surface withstand voltage in vacuum[J], IEEE Trans. On electrical insulation, 1988, vol. 23(1): 57～61
[46] Hatfield L Let al. A treatment which improves surface withstand voltage in vacuum[J]. IEEE Trans electrical insulation, 1985, 23～57
[47] Brettschneider H., improving the high voltage quality of alumina insulators n vacuum by surface doping[J]. IEEE Trans electrical insulation, 1988: 23～33
[48] J. Juchniewicz et al., The effect of the number of spacer insulators on the breakdown voltage of vacuum insulation[J], IEEE Trans. Electrical insulation, 1979, vol. 14: 107～110.
[49] Milton O., pulsed flashover of insulators in vacuum[J], IEEE Trans, on electrical insulation, 1972, 7(1): 9～15
[50] Tumiran et al., flashover from surface charge distribution on alumina insulators in vacuum[J], IEEE Trans. On dielectrics and electrical insulation, 1997, 4(4): 400～406.
[51] Akahane M, Kanda K, Yahagi K, Effect of dielectric constant on surface discharge of polymer insulators in vacuum[J]., Journal of applied physics, 1973, 44(6): 2927
[52] Liu F, et al. Surface resistivity tailoring of ceramics by metal ion implantation., surface and coatings technology, 1998, 46～51, 103～104.
[53] 谢．彼．布加耶夫等，相对论多波超高频发生器[M]，中国工程物理研究院，绵阳：99
[2] Vlieks A E, Allen A, Callm R S. et al. Breakdown phenomena in high-power klystrons. IEEE Trans. On Electrical Insulation, 1989, 24(6): 1023～1028.
[3] Saito Y, Michizuo N, Anami S. et al. Surface flashover on alumina RF windows for high-power use. IEEE Trans. On Electrical Insulation, 1993, 24(4): 566～573.
[4] T. H. Martin et al. J. C. Martin on Pulse Power, New York, Plenum Press, 1996: 258.
[5] H. Craig Miller, Flashover of Insulators in Vacuum, IEEE Trans. Insul., 1993, Vol. 28: 512～527.
[6] S. E. Sampayan et al. Multilayer. High Gradient Insulator Technology,. IEEE Trans on Dielectrics and Electrical Insulation, Vol. 7(3): 334～339.
[7] 张冠军．真空中固体绝缘材料沿面闪络的起始机理与发展过程[D]．博士学位论文．西安：西安交通大学，2001．
[8] 丁立键，李成榕．真空中绝缘子的沿面闪络现象[J]．高电压技术，1999，25(2)：53～57．
[9] H. H. Zhong. Time characteristics of fast pulsed flashover in vacuum[J]. IEEE Trans on electrical insulation, 1992, vol.27(3): 496～503
[10] R. A. Anderson and J. P. Brainard. Mechanism of Pulsed Surface Flashover Involving Electron-stimulated Desorption [J-]. J. Appl. Phys., 1980, Vol. 51: 1414～1421.
[11] G. Blaise and C. Le Gressus, Charging and Flashover Induced by Surface Polarizetion Telaxation Process [J]. J. Appl. Phys., 1991, Vol. 69, 6334～6339.
[12] G. Blaise, New approach to flashover in dielectrics based on a polarization energy relaxation mechanism[J], IEEE trans. On Electrical Insulation, 1993, Vol. 28(4): 437～443
[13] P. A. Amold et al. 45degree insulator surface flashover a review and new results[A], VIIth. International Symposium on Discharges and Electrical Insulation in Vacuum: 231
[14] 孙大明，席光康，固体的表面与界面[M]，合肥，安徽教育出版社，1996
[15] E. A. Burke, Secondary emission from polymers[J], IEEE Trans on Nuclear Science, 1980, Vol. NS-27(6): 1760～1764.
[16] De Tourreil C H., Srivastave K D. Mechanusm of surface charging of high-voltage insulators in vacuum [J]. IEEE Trans. on electrical insulation, 1973, 8(1): 17-21.
[17] O. Yamamoto et al. Monte carlo simulation of surface charge on angled insulators in vacuum [J], IEEE Trans. on electrical insulation, 1993, vol. 28(4): 706～712.
[18] B H W Hendriks et al.. Modes in electron-hopping transport iver insulators sustained by secondary electron emission [J], J. phys. D: Appl. Phys. 30, 1997: 1252～1254.
[19] Ningsheng Xu et al.. Effects of geometry and polarity on the prebreakdown and flashover behavior of conical high-voltage insulators in vacuum [J], IEEE Trans. On plasma science, 1997, vol. 25(3): 447～454.
[20] Z. Nadolny, W. Ziomek. Field stress control for spacer in vacuum using varied geometry of triple junction [D], XVIIth international symposium on discharges and electrical insulation in vacuum, Berkeley, 1996: 527～531.
[21] G. Damamme, C. Le gressus, Simulation of the triple junction eggects in vacuum devices [D],1996 IEEE Annual Report-conference on electrical insulation and dielectric phenomena, San Franciscao, 1996: 562～566.
[22] T. S.Sudarshan, Electrode architecture related to surface flashover of solid dielectrics in vacuum[J],
IEEE trans, on dielectrics and electrical insulation, 1997, vol.4(4): 374～381.
[23] A. Sivathanu Pillai and Reuben Hackam. Influence of metal-insulator junction on surface flashover in vacuum [J-I, J. Appl. Phys. 1987, 61(11), 4992～4999
[24] I. D. Chalmers et al. Surface charging and flashover on insulators in vacuum [J], IEEE Trans. On dielectrics and electrical insulation, 1995, vol. 2(2): 225～230
[25] O. Yamamoto et al. Effects of spark conditioning, insulator angle and length on surface flashover in vacuum [j], IEEE Trans. Electrical insulation, 1989, vol. 24: 991～994
[26] A. S. Pillai and R. Hackam, Surface flashover of conical insulator in vacuum[J], J.appl.Phys,,1984,vol 56: 1374～1381
[27] A. Watson, Pulsed flashover in vacuum,[J], J.Appl. Phys., 1967, vol.38: 2019～2023
[28] O. Milton, Pulsed flashover of insulators in vacuum [J], IEEE Trans. Electrical insulation, 1972, vol. 7: 9～15
[29] J. Golen and C. A. Kapertanakos, Flashover breakdown of an insulator in vacuum by a voltage impulse in the presence of a magnetic field [J], J. Appl. Phys., 1977, vol. 48: 1756～1758.
[30] N. C. Jaitly and T. S. Sudarshan. Novel insulator designs for superior dc hold-off in bridhed vacuum gaps [J], IEEE Trans. electrical Insulation, 1987, vol. 22: 801～810.
[31] R. Lee et al. Predischarge current measurements in vacuum gaps bridged with pleciglas insulators[J], IEEE Trans. Electrical insulation., 1983, vol. 18: 280～286.
[32] Pillai A s, Hackam R. Surface flashover of solid dielectric in Vacuum [J], Journal of Applied Physics, 1982, 53(4): 2983～2987.
[33] Ian D. Smith, Flashover of vacuum interfaces with many stages and large transit times [J], IEEE Trans. On plasma science, 1997, vol. 25(2): 293～299.
[34] R. A. Anderson, Mechanism of fast surface flashover n vacuum[J], Appl. Ohys. Lett., 1974, vol.24: 54～56.
[35] R. Korzekwa et al., Inhibiting surface flashover of space conditions using magnetic fields [J], IEEE Trans. Plasma Sci., 1989,vol. 17: 612～615.
[36] J. P. Vandevender et al., magnetic inhibition of insulator flashover [J], J. appl. Phys., 1982, vol.53: 4441～4447
[37] Miller H C., Flashover of insulators in vacuum, reviews of the phenomena and techniques to improver holdoff voltage [J], IEEE Trans. On electrical insulation, 1993, 28(4): 512～527.
[38] Pillai A s, Hackam R. Surface flashover of solid insulators in atmospheric air and in vacuum[J]. Journal of applied physics, 1985, 58(1): 146～153.
[39] C. Le Gressus et al. Flashover in wide-band-gap high-purity insulators: methodology and mechanisms [J], J. appl. phys., 1991, vol. 69: 6325～6333
[40] S. Grzybowski et al., Electric surface strength and surface deterioration of thermoplastic insulators in vacuum[J], IEEE Trans. Electric insulation, 1983, vol. 18: 301～309.
[41] R. A. Anderson, Propagation velocity of cathode-initiated surface flashover [J], J. appl. phys., 1977, vol. 48: 4210～4214.
[42] J. D. Cross, High speed photography of surface flashover of dielectrics in a strong electric field [D], Proc. ⅩⅣ Int. Sym. Discharge electric insulation of Vacuum, Santafe, 1990, 365～367.
[43] J. E. Thompson et al., Investigations of fast insulator surface flashover in vacuum [J], IEEE Trans. Plasma Sci., 1980, vol. 8: 191～197.
[44] Tangal S. Sudarshan, The effect of chromium oxide coatings on surface flashover of alumina spacers in vacuum [J], IEEE Trans. On electrical insulation, 1976, vol. EI-11: 32～35.
[45] L. L. Hatfield et al. a treatment which improves surface withstand voltage in vacuum[J], IEEE Trans. On electrical insulation, 1988, vol. 23(1): 57～61
[46] Hatfield L Let al. A treatment which improves surface withstand voltage in vacuum[J]. IEEE Trans electrical insulation, 1985, 23～57
[47] Brettschneider H., improving the high voltage quality of alumina insulators n vacuum by surface doping[J]. IEEE Trans electrical insulation, 1988: 23～33
[48] J. Juchniewicz et al., The effect of the number of spacer insulators on the breakdown voltage of vacuum insulation[J], IEEE Trans. Electrical insulation, 1979, vol. 14: 107～110.
[49] Milton O., pulsed flashover of insulators in vacuum[J], IEEE Trans, on electrical insulation, 1972, 7(1): 9～15
[50] Tumiran et al., flashover from surface charge distribution on alumina insulators in vacuum[J], IEEE Trans. On dielectrics and electrical insulation, 1997, 4(4): 400～406.
[51] Akahane M, Kanda K, Yahagi K, Effect of dielectric constant on surface discharge of polymer insulators in vacuum[J]., Journal of applied physics, 1973, 44(6): 2927
[52] Liu F, et al. Surface resistivity tailoring of ceramics by metal ion implantation., surface and coatings technology, 1998, 46～51, 103～104.
[53] 谢．彼．布加耶夫等，相对论多波超高频发生器[M]，中国工程物理研究院，绵阳：99