The tokamak hybrid scenario, a combination of the inductive current drive and the non-inductive current drive, aims at high neutron fluence and a long pulse length for the ITER engineering test towards DEMO. It has been reported experimentally that the concentration of current density, J, peculiar to inductive discharges, was much smaller than that of a simple estimation. We propose a new model to explain the above observations: the central core plasma column can be non-axisymmetric due to the m/n = 1/1 MHD-mode deformation (m and n are poloidal and toroidal mode numbers, respectively). The neo-classical resistivity is enhanced, and the diagnostics are affected. An internal kink mode is a candidate of this instability. Compared with the JT-60U experiment, the reconstructed J profile agrees well with the calculated J profile including the enhanced neo-classical resistivity.
Impact of ideal MHD stability limits on high-beta hybrid operation