On the electron sheath theory and its applications in plasma–surface interactions  

作　　者：Guangyu SUN Shu ZHANG Anbang SUN Guanjun ZHANG 孙光宇;张舒;孙安邦;张冠军(State Key Laboratory of Electrical Insulation and Power Equipment,School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,People’s Republic of China;Ecole Polytechnique Fédérale de Lausanne,Swiss Plasma Center,CH-1015 Lausanne,Switzerland;Laboratoire de Physique des Plasmas,Ecole Polytechnique,91120 Palaiseau,France)

机构地区：[1]State Key Laboratory of Electrical Insulation and Power Equipment,School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,People’s Republic of China [2]Ecole Polytechnique Fédérale de Lausanne,Swiss Plasma Center,CH-1015 Lausanne,Switzerland [3]Laboratoire de Physique des Plasmas,Ecole Polytechnique,91120 Palaiseau,France

出　　处：《Plasma Science and Technology》2022年第9期52-67,共16页等离子体科学和技术（英文版）

基　　金：the auspices of National Natural Science Foundation of China(Nos.51827809,52077169);the National Key R&D Program of China(No.2020YFC2201100)。

摘　　要：In this work,an improved understanding of electron sheath theory is provided using both fluid and kinetic approaches while elaborating on their implications for plasma–surface interactions.A fluid model is proposed considering the electron presheath structure,avoiding the singularity in electron sheath Child–Langmuir law which overestimates the sheath potential.Subsequently,a kinetic model of electron sheath is established,showing considerably different sheath proflles in respect to the fluid model due to non-Maxwellian electron velocity distribution function and flnite ion temperature.The kinetic model is then further generalized and involves a more realistic truncated ion velocity distribution function.It is demonstrated that such a distribution function yields a super-thermal electron sheath whose entering velocity at the sheath edge is greater than the Bohm criterion prediction.Furthermore,an attempt is made to describe the electron presheath–sheath coupling within the kinetic framework,showing a necessary compromise between a realistic sheath entrance and the inclusion of kinetic effects.Finally,the secondary electron emissions induced by sheath-accelerated plasma electrons in an electron sheath are analysed and the influence of backscattering is discussed.

关 键 词：plasma–surface interaction plasma sheath secondary electron emission Child–Langmuir law 

分 类 号：O53[理学—等离子体物理]