Study of Finite-Orbit-Width Effect on Neoclassical Transport in Tokamak Core Region

Neoclassical transport simulation using the δ f Monte-Carlo method is carried out to investigate the finite-orbitwidth (FOW) effect on the transport near the magnetic axis. The time evolution of the radial electric field to maintain the ambipolarity of the flux is calculated simultaneously. It is found that, in the near-axis region, the ion heat flux decreases from the value predicted by the standard neoclassical theory both in the banana and plateau regimes. Though the radial transport shows a strong dependence on the FOW effect, the ambipolar electric field profile at the steady state is similar to that calculated in the small-orbit-width limit approximation