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将麦克斯韦方程组和简化等离子体方程耦合求解, 对介质表面附近大气击穿形成等离子体的过程进行了理论研究. 分别使用一维、二维模型对等离子体的形成过程及等离子体对电磁波的反射、吸收过程进行了模拟研究. 一维计算结果发现在ne = 0, j = 0两种边界条件下, 虽然形成的等离子体密度分布相差较大, 但二者得到的微波反射、吸收、透射波形彼此相差不大. 初始电子数密度厚度为20 mm的条件下, 得到界面附近的等离子体密度大于5 mm厚度的情况. 二维计算结果发现, 由于TE10模在波导中心位置处的微波电场最强, 电子碰撞电离首先在中心位置处形成等离子体, 当等离子体密度达到一定值(临界密度附近)时, 波导中心介质表面处微波场强减小, 等离子体区域沿着介质表面向两侧移动. TE10模在波导边缘处微波电场强度小于击穿阈值, 因此等离子体区域不可能移动到波导边缘附近.Microwave air breakdown at dielectric surface is investigated by numerically solving the fluid-based plasma equations coupled with the Maxwell equations. The plasma formation and microwave scattering and absorption by plasma are investigated by one-dimensional (1D) and two-dimensional (2D) models. In the 1D model, it is found that at the initial stage of microwave breakdown, the plasma develops in the whole plasma region. As time increases, the plasma in the upstream grows much faster than in the downstream. Although the electron density distributions for ne = 0 and j = 0 are different, the microwave reflection, absorption and transmission are almost the same. It is found that the electron number density in the upstream region for 20 mm is larger than for 5 mm. In the 2D model, it is found for TE10 mode that the plasmoid first grows in the middle of waveguide until its density becomes large enough to diffract the incident field, then the plasma region moves along the surface to both sides. The plasma region cannot reach the wall of waveguide, where the electric field is smaller than the breakdown threshold. After comparison between the computational and experimental results, it is found that the simulated absorbed power is larger than the measured one, and the transmitted power is smaller than than measured one. The reason is that the initial electron densities in 1D and 2D simulation are both assumed to cover the whole dielectric surface, but the plasma in experiment develops in a very small region.
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Keywords:
- dielectric surface /
- microwave air breakdown /
- numerical simulation
[1] Gurevich A, Borisov N, Milikh G 1997 Physics of Microwave Discharges (New York: Gordon and Breach)
[2] Barker R J, Schamiloglu E 2001 High Power Microwave Sources and Technologies (New York: Institute of Electrical and Electonics Engineers, Inc.)
[3] Kim H C, Verboncoeur J P 2005 Phys. Plasmas 12 123504
[4] Neuber A A, Krile J T, Edmiston G F, Krompholz H G 2007 Phys. Plasmas 14 057102
[5] MacDonald A D 1966 Microwave Breakdown in Gases (New York: John Wiley & Sons)
[6] Ford P J, Beeson S R, Krompholz H K, Neuber A A 2012 Phys. Plasmas 19 073503
[7] Foster J E 2012 Ph. D. Dissertation (Lubbock: Texas Technical University)
[8] Aleksandrov K V, Grachev L P, Esakov I I, Khodataev K V 2002 Tech. Phys. 47 851
[9] Aleksandrov K V, Shibkov V M, Shibkova L V 2008 Moscow Univ. Phys. Bull. 63 365
[10] Boeuf J P, Chaudhury B, Zhu G Q 2010 Phys. Rev. Lett. 104 015002
[11] Zhou Q H, Dong Z W, Chen J Y 2011 Acta Phys. Sin. 60 125202 (in Chinese) [周前红, 董志伟, 陈京元 2011 物理学报 60 125202]
[12] Zhou Q H, Dong Z W 2013 Acta Phys. Sin. 62 205201 (in Chinese) [周前红, 董志伟 2013 物理学报 62 205201]
[13] Zhou Q H, Dong Z W 2011 Appl. Phys. Lett. 98 161504
[14] Cummer S A 1997 IEEE Trans. Antennas Propagat. 45 392
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[1] Gurevich A, Borisov N, Milikh G 1997 Physics of Microwave Discharges (New York: Gordon and Breach)
[2] Barker R J, Schamiloglu E 2001 High Power Microwave Sources and Technologies (New York: Institute of Electrical and Electonics Engineers, Inc.)
[3] Kim H C, Verboncoeur J P 2005 Phys. Plasmas 12 123504
[4] Neuber A A, Krile J T, Edmiston G F, Krompholz H G 2007 Phys. Plasmas 14 057102
[5] MacDonald A D 1966 Microwave Breakdown in Gases (New York: John Wiley & Sons)
[6] Ford P J, Beeson S R, Krompholz H K, Neuber A A 2012 Phys. Plasmas 19 073503
[7] Foster J E 2012 Ph. D. Dissertation (Lubbock: Texas Technical University)
[8] Aleksandrov K V, Grachev L P, Esakov I I, Khodataev K V 2002 Tech. Phys. 47 851
[9] Aleksandrov K V, Shibkov V M, Shibkova L V 2008 Moscow Univ. Phys. Bull. 63 365
[10] Boeuf J P, Chaudhury B, Zhu G Q 2010 Phys. Rev. Lett. 104 015002
[11] Zhou Q H, Dong Z W, Chen J Y 2011 Acta Phys. Sin. 60 125202 (in Chinese) [周前红, 董志伟, 陈京元 2011 物理学报 60 125202]
[12] Zhou Q H, Dong Z W 2013 Acta Phys. Sin. 62 205201 (in Chinese) [周前红, 董志伟 2013 物理学报 62 205201]
[13] Zhou Q H, Dong Z W 2011 Appl. Phys. Lett. 98 161504
[14] Cummer S A 1997 IEEE Trans. Antennas Propagat. 45 392
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