Particle Flow and Dynamic Response of Potential Formation at the Plug Region of a Tandem Mirror

点击翻译按钮获取中文摘要

The objective of this research is understanding of the mechanism of the plug potential formation through investigation of the change of particle flow at the plug region of a tandem mirror associated with electron heating. In this year, dynamic variation of the potential structure from the plug region to the end plate during electron cyclotron resonance heating (ECRH) has been studied. Main results are as follows.(1) It has been found that potential formation by the plug ECRH is a dynamic process in which the density distribution and the change of the potential is closely linked. Moreover, the plug potential gears with the end plate potential. This means that the end plate potential has a large influence on the plug potential as measured from the vacuum vessel.(2) We have presented a model of an equivalent circuit that includes the current distribution from the plug/barrier region to the end plate and potential structure. The role of the plug ECRH is generation of the electromotive force in this circuit. This electromotive force is divided into the plug potential and the negative end plate potential according to the values of the effective resistance from each region to the vacuum vessel.(3) The current in this circuit flows through the sheath region on front of the end plate. The analysis of the end plate potential from the viewpoint of a current carrying sheath has confirmed the validity of our potential model.(4) Theoretical studies have been carried out along with the above investigations. We have succeeded to develop a potential model that includes the temperature anisotropy as a result of ECRH and the modified Boltzmann relation. This model correctly predicts the dynamic behavior of the potential creation. The importance of the Coulomb collisions for continuity of the axial potential profile near the plug region has been pointed out.