Abstract：The inductively coupled plasma (ICP) has more advantages over other plasma sources in radar stealth, including simple antenna structure, a wide pressure range, large area and high electron density. Compared with the open-type plasma, closed-type plasma is more compatible with the flying environment of aircraft, where the air flows fast and pressure changes fiercely. A newly designed cylindrical closed chamber made of quartz windows inlaid in stainless steel was used to generate planar ICP for the potential application in stealth design of aircraft local. Compared with previous all-quartz chamber, the new structure effectively improved the homogeneity of ICP because of the ground connection. The discharging characteristics and emission spectrum of ICP in the closed chamber was studied. Obvious E-H mode transition was observed when the power came to 150 W in experiment. The spectrum intensity and electron density increased in a huge step at the transition point. Over the whole discharging progress, the spectrum intensity increased with power, but because of the diversity in transition probability and excitation energy of spectral lines, the increasing amplitude was also different. Based on the emission spectrum of ICP, the electron excitation temperature was diagnosed by the Boltzmann slope method. The electron excitation temperature was above 2 000 K and the higher of the power, the lower of the temperature. Because higher power enhanced the thermal motion of electrons and then the collision between particles became fiercer. This kind of collision consumed more energy so the temperature came down. The distribution of electron excitation temperature along the radial direction was approximately homogeneous. And the power had little influence on the distribution. A Voigt convolution function was introduced to solve the problem of big error and cockamamie calculation about spectrum diagnosis of electron density. The interferential broadenings of argon emission spectrum were eliminated by fitting calculation. So the accurate full width at half maximum of Stark broadening was obtained. Then the electron density was calculated by Stark broadening method. The peak electron density came to 7.5×1017 m-3 at the center of chamber. The electron density increased with power because the coupling efficient was enhanced. Power had little influence on the spatial distribution of electron density.
Key words：Plasma stealth; Inductively coupled plasma; Emission spectra; Electron excitation temperature; Electron density
[1] Wei Xiaolong, Xu Haojun, Li Jianhai, et al. Journal of Applied Physics, 2015, 117(20): 203301.
[2] CHENG Jia, JI Lin-hong, ZHU Yu(程 嘉，季林红，朱 煜). Journal of Tsinghua University(清华大学学报), 2010, 50(2): 250.
[3] DI Xiao-lian, XIN Yu, NING Zhao-yuan(狄小莲，辛 煜，宁兆元). Acta Physica Sinica(物理学报), 2006, 55(10): 5311.
[4] GAO Peng, CHEN Jun-fang, FENG Jun-qin(高 鹏，陈俊芳，冯军勤). The Journal of Light Scattering(光散射学报), 2013, 25(3): 297.
[5] WEI Xiao-long, XU Hao-jun, LIN Min，et al(魏小龙，徐浩军，林 敏，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2016, 36(4): 1170.
[6] WEI Xiao-long, XU Hao-jun, LI Jian-hai，et al(魏小龙，徐浩军，李建海，等). Acta Physica Sinica(物理学报), 2015, 64(17): 175201.
[7] Lin Min, Xu Haojun, Wei Xiaolong, et al. Plasma Science and Technology, 2015, 17(10): 847.
[8] Liu Qiuyan, Li Hong, Chen Zhipeng, et al. Plasma Science and Technology, 2011, 13(4): 451.
[9] Jamroz P，Zyrnicki W. Vacuum, 2008, 82(6): 651.
[10] Vladimir N. Ochkin Spectroscopy of Low Temperature Plasma. Russia: Wiley-VCH, 2009, 03.
[11] Joshi N K, Sahasrabudhe S N, Sreekumar K P, et al. The European Physical Journal D-Atomic, Molecular, Optical and Plasma Physics, 2003, 26(2): 215.
[12] Griem H R. Plasma Spectroscopy. New York: McGraw-Hill Book Company, 1964.
[13] Griem H R. Physical Review, 1962, 128(2): 515.
[14] Finn G D, Mugglestone D. Monthly Notices of the Royal Astronomical Society, 1965, 129(2): 221.
[15] Ganapathy S, Parthasarathi V. Indian Journal of Pure and Applied Physics, 1977, 15(2): 63.
