Revisiting the improved core confinement simulations for FT‐2 tokamak

Abstract

In the present paper, we revisit observations performed in FT-2 tokamak from previous works. Improvements of core confinement are observed and believed to be caused by wide orbits going from collisionless to collisional regimes. Similar phenomena can occur whenever gradient lengths are comparable to the orbit widths at the top of the pedestal and the loss cone is continuously and increasingly filled by heated particles, collisions and turbulent effects. The lower hybrid heating operator is introduced into the ELMFIRE code to increase the ion temperature during the simulations while keeping the edge temperature low with logical boundary condition at the limiter. Particular focus is given on how the radial electric field deviates from the neoclassical value while introducing turbulent effects.

Numerical study of limits of neoclassical theory in the plateau regime in the presence of impurities

“…Such resolution enables the study of density poloidal variations effects affecting the conventional neoclassical physics while prohibiting turbulence growth as the proper scales are not resolved. At the same time, loop voltage and LH heating which were used in heated cases [ 22 ] are here turned off to investigate the quasi‐stationary state development of the neoclassical radial electric field. In the present manuscript, the impurity concentration was selected to have similar α ‐parameter values as in Ref.…”