A closed divertor configuration for reduction of the heat load and efficient particle control for helical fusion reactors

摘要

An innovative closed helical divertor concept is proposed for reduction of a heat load on the divertor plates and efficient particle control/pumping. The closed divertor configuration is investigated by a neutral particle transport simulation code coupled with a one-dimensional plasma fluid analysis on the divertor legs for a helical fusion reactor in which the geometry of the plasma and the magnetic field line configuration is same as that in the large helical device (LHD). The closed divertor configuration practically utilizes intrinsic three-dimensional magnetic field line configurations in the plasma periphery (an ergodic layer and divertor legs). The divertor configuration is optimized to an inward shift magnetic configuration in which the best energy confinement time has been achieved, a highly ergodized magnetic field line structure is formed in the inboard side of the torus, and the neutral density there is higher than that in the other region in the LHD vacuum vessel. It means that the divertor configuration is compatible with good main plasma confinement, effective divertor heat load reduction and efficient particle control/pumping from the inboard side. The analysis in this closed helical divertor configuration shows many advantageous over that in the other divertor concept