Radial electric field formation by the gyrocenter shifts of the charge exchange reactions at the boundary of fusion device

Abstract

As an important future energy source nuclear fusion researchers have been trying to solve the problem of radial electric field formation: the key factor of H-mode (high confinement mode) phenomena. Although a profound analysis has been developed on the turbulence suppression by E×B flow (E is the electric field and B is the magnetic field) as a basic mechanism of H-mode transition, the origin of the electric field and its relation with the neutrals are not fully explained. In this paper a novel model of radial electric field formation achieved by gyrocenter shifts during the charge exchange reactions and ion elastic scatterings with the neutrals is analyzed. From this analysis the formula of radial current density by the poloidal momentum sink at the reactions of charge exchange with boundary neutrals is developed with an example calculation for a given plasma condition similar to the experiment. The profile and absolute value of the saturated radial electric field are in agreement with the experimental results. An H-mode transition scenario is discussed by the gyrocenter shift model.