Presheath profiles in simulated tokamak edge plasmas
Presheath profiles in simulated tokamak edge plasmas
复制标题
模拟托卡马克边缘等离子体中的预护套轮廓
DOI：
10.1016/0022-3115(89)90288-2
复制
发表时间：
1989
影响因子：
3.1
通讯作者：
K. Chung
中科院分区：
文献类型：
--
作者：
B. LaBombard;R. Conn;Y. Hirooka;R. Lehmer;W. Leung;R. Nygren;Y. Ra;G. Tynan;K. Chung
PISCES实验产生的稳态磁化等离子体被用来研究与托卡马克等约束装置有关的等离子体-壁相互作用现象。本文报道了从壁面沿沿着磁力线进入“模拟托卡马克”边缘等离子体的预鞘区的实验研究。专门为这项工作开发的诊断包括快速扫描多朗缪尔/发射/马赫探针系统和CID相机成像系统。密度、电子温度、浮动电位、空间电位和体等离子体流速的测量已经在等离子体中获得，密度范围从10 12到10 13 cm-3，电子温度从5到15 eV。和0.2至1.4kG的轴向磁场。等离子体密度分布沿着磁场通常显示出朝向壁表面减小的特征因子2。等离子体电位的变化，在附近的预鞘区的顺序为0.5 T e的测量，一致的散装等离子体流接近的离子声速附近的壁面，从一个简单的“自由落体”模型推断。一个玻尔兹曼模型的前鞘密度分布的准确性跟踪的马赫探针和光谱手段测量的密度分布。流动剖面被用作各种磁化马赫探针理论的一致性检查。结果表明，通过粘度的平行动量的跨场输运在PISCES等离子体中相对不重要，因此在托卡马克边界层等离子体中可能不重要。非热电子放电显示空间电位和浮动电位的轴向分布，这表明壁表面附近的“较热”的电子分布函数，与“较冷”的电子被反射的预鞘电位降一致。
Steady state magnetized plasmas produced by the PISCES experiment are used to study plasma-wall interaction phenomena relevant to confinement devices such as tokamaks. An experimental investigation of the presheath region that extends from a wall surface into “simulated tokamak” edge plasmas along magnetic field lines is reported. Diagnostics especially developed for this work include a fast-scanning multiple Langmuir/Emissive/Mach probe system and a CID camera imaging system. Measurements of density, electron temperature, floating potential, space potential, and bulk plasma flow velocities have been obtained in plasmas with densities ranging from 10 12 to 10 13 cm− 3, electron temperatures from 5 to 15 eV. and axial magnetic fields of 0.2 to 1.4 kG. Plasma density profiles along the magnetic field typically show a characteristic factor of 2 decrease towards the wall surface. A plasma potential variation in the near presheath zone of order 0.5 T e is measured, consistent with the bulk plasma flow approaching the ion sound speed near the wall surface, as inferred from a simple “free fall” model. A Boltzmann model for the presheath density profile accuracy tracks the density profile measured both by the Mach probe and by spectroscopic means. Flow profiles are used as a consistency check on various magnetized Mach probe theories. Results suggest that cross-field transport of parallel momentum through viscosity is relatively unimportant in PISCES plasmas and thus may be unimportant in tokamak boundary layer plasmas. Discharges with non-thermal electrons display axial profiles of space potential and floating potential which indicate a “hotter” electron distribution function near the wall surface, consistent with “colder” electrons being reflected by the presheath potential drop.