Fast-ion transport in advanced tokamak scenarios with qmin close to two at ASDEX Upgrade

摘要

Steady-state operation of tokamaks is demanding since the toroidal plasma current needs to be sustained by non-inductive means [1]. Although external current drive sources are available, their extensive use would yield an unacceptably high recirculated power fraction in future fusion power plants. High fractions of the intrinsic bootstrap current are needed that can be obtained in discharges with off-axis current distributions (low central poloidal fields) and internal transport barriers (strong gradients). Such advanced discharge conditions are, however, difficult to maintain since they are prone to impurity accumulation [2] and ideal ideal magnetohydrodynamic (MHD) modes[3].