弱电离大气等离子体电子能量分布函数的理论研究
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摘要
使用球谐展开的方法求解玻尔兹曼方程,得到了弱电离大气等离子体(79%氮气和21%的氧气)的电子能量分布函数(EEDF).发现当约化电场较小时(E/N<100Td),EEDF在2—3eV急剧下降,在此情况下,高能尾部比麦氏分布要小;当约化电场增加,E/N>400Td,分布函数趋近于麦氏分布;当约化电场进一步增加,E/N>2000Td,EEDF的高能尾部(超过200eV)相对于麦氏分布增加.在高频场作用下,EEDF更倾向于麦氏分布.当ω﹤﹤vm时,有效电子温度只依赖于E/ω,而与碰撞频率无关;当ω>>vm时,有效电子温度只依赖于E/N,与微波频率无关.与一些单原子分子等离子体中电子-电子碰撞在电离度大于106时就会影响EEDF不同,空气等离子体中,只有当电离度大于0.1%时,电子-电子碰撞才会对EEDF有明显影响.
The electron energy distribution function (EEDF) of weakly ionized air plasma (79% nitrogen and 21% oxygen) is investigated by solving the Boltzmann equation with the spherical harmonics expansion. It is found that the EEDF deceases sharply in an energy range from 2 to 3 eV for low reduced field (E/N < 100 Td), and the high energy tail of the EEDF decreases more sharply than Maxwell distribution. When the reduced field increases to a range 400 to 2000 Td, the EEDF approaches to Maxwell distribution. When the reduced field is greater than 2000 Td, the high energy tail (>200 eV) of the EEDF deceases more slowly than Maxwell distribution. It is shown that the EEDF approaches to Maxwell distribution in a high frequency field. The effective electron temperature is dependent only on E/ω for ω<>vm . The electron-electron collisions play no significant role until the ionization degree is bigger than 0.1%. This is different from the case of monatomic plasmas, in which the EEDF is influenced by electron-electron collisions for ionization degree greater than 10-6 .
The electron energy distribution function (EEDF) of weakly ionized air plasma (79% nitrogen and 21% oxygen) is investigated by solving the Boltzmann equation with the spherical harmonics expansion. It is found that the EEDF deceases sharply in an energy range from 2 to 3 eV for low reduced field (E/N < 100 Td), and the high energy tail of the EEDF decreases more sharply than Maxwell distribution. When the reduced field increases to a range 400 to 2000 Td, the EEDF approaches to Maxwell distribution. When the reduced field is greater than 2000 Td, the high energy tail (>200 eV) of the EEDF deceases more slowly than Maxwell distribution. It is shown that the EEDF approaches to Maxwell distribution in a high frequency field. The effective electron temperature is dependent only on E/ω for ω<
引文
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[2]Becker K H,Kogelschatz U,Schoenbach K H,Barker R J2005Non-Equilibrium Air Plasma at Atmosphere Pressure(London:IOP pub-lishing)
[3]Starikovskaia S M2006J.Phys.D:Appl.Phys.39R265
[4]Siefert N S2007Phys.Fluids19036102
[5]Kuo S P2006Phys.Plasmas13033505
[6]Chang C,Liu G Z,Zhu X X,Chen H B,Yang J Y2009Phys.Plasmas16033505
[7]Krile J T,Neuber A A,Krompholz H G,Gibson Thomas L2006Appl.Phys.Lett.89201501
[8]Dijk J V,Peerenboom K,Jimenez M,Mihailova D,Mullen J V D2009J.Phys.D:Appl.Phys.42194012
[9]Kusher M J20092009J.Phys.D:Appl.Phys.42194013
[10]Kim H C,Iza F,Yang S S,Radmilovic-Radjenovic M,Lee J K2005J.Phys.D:Appl.Phys.38R283
[11]Zhou Q H,Dong Z W,Chen J Y2011Acta Phys.Sin.60125202(in Chinese)[周前红,董志伟,陈京元2011物理学报60125202]
[12]Nam S K,Verboncoeur J P2008Appl.Phys.Lett.99231502
[13]Nam S K,Lim C,Verboncoeur J P2009Phys.Plasmas16023501
[14]Capitelli M,Ferreira C M,Gordiets B F,Osipov A I2001Plasma Ki-netics in Atmospheric Gases(Berlin:Springer)
[15]Hagelaar G J M,Pitchford L C2005Plasma Souces Sci.Technol.14722
[16]Trunec D,Bonaventura Z,Necas D2006J.Phys.D:Appl.Phys.392544
[17]Phelps A V,Pitchford L C1985Phys.Rev.A312932
[18]Pitchford L C,Oneil S V,Rumble Jr J R1981Phys.Rev.A23294
[19]ItikawaY,Hayashi M,Ichimura A,Onda K,Sakimoto K,Takayanagi K1986J.Phys.Chem.Ref.Data15985