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Kinetic Analyzes of Potential Formation and Transport in Boundary Plasmas

边界等离子体中电势形成和传输的动力学分析

基本信息

批准号：
06680483
负责人：
SATO Kunihiro
金额：
$ 1.22万
依托单位：
Himeji Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

1. Two formaiton mechanisms of the magnetic presheath are clarified by kinetic analyzes. The magnetic presheath in a cold-ion plasma is formed due to the ion polarization drift, and that in a hot-ion plasma is due to the finite ion-gyroradius effect. An oblique magnetic field has two means of preventing secondary electrons from flowing into a plasma. One is the reflection of secondary electrons by the Lorentz force, which is effective when the Debye length is much larger than the electron gyroradius. Another is enhancement of the space-charge effect in the sheath due to formation of the magnetic presheath. The magnetic presheath acts as a thermal insulator instead of the sheath under conditions of the space-charge limitation.2. Kinetic analyzes have been carried out to study impurity control effects of a spatially expanding magnetic field and effects of neutral-gas collisions on power transmission in the divertor chamber. The spatial variation of magnetic field strength causes an electrostatic potential drop along the magnetic field lines, which decreases with increasing plasma-neutral collision frequency. Cold ions of fuel and ionized impurities are successfully trapped in the divertor by the electrostatic potential if the ionization rate does not exceed an upper limit. Charge exchange replaces energetic ions by cold ions, and amplification of the ion flux by ionization reduces the electrostatic potential drop. Consequently, plasma-neutral collisions markedly reduce the impact energy of ions reaching the divertor plates. Low values of the power transmission factor as low as 2-3 measured in tokamak experiments can mainly be due to reduction of ion energy through plasma-neutral interaction processes in the divertor.

1.通过动力学分析阐明了磁性预鞘的两种形成机制。冷离子等离子体中的磁预鞘是由于离子极化漂移而形成的，而热离子等离子体中的磁预鞘是由于有限离子回转半径效应而形成的。倾斜磁场有两种防止二次电子流入等离子体的方法。一是洛伦兹力对二次电子的反射，当德拜长度远大于电子回转半径时有效。另一个是由于磁性预护套的形成而增强了护套中的空间电荷效应。在空间电荷限制条件下，磁性预护套代替护套起到热绝缘体的作用。 2．进行了动力学分析，以研究空间扩展磁场的杂质控制效应以及中性气体碰撞对偏滤器室中功率传输的影响。磁场强度的空间变化导致沿磁场线的静电势下降，该势随着等离子体中性碰撞频率的增加而减小。如果电离率不超过上限，则燃料的冷离子和电离杂质被静电势成功地捕获在偏滤器中。电荷交换用冷离子代替高能离子，并且通过电离放大离子通量减少了静电势降。因此，等离子体中性碰撞显着降低了到达偏滤器板的离子的冲击能量。托卡马克实验中测得的功率传输系数低至 2-3，这主要是由于偏滤器中的等离子体-中性相互作用过程降低了离子能量。