Critical assessment of ion loss mechanisms for L-H transition

Monte Carlo ion simulation of the tokamak edge, based on the neoclassical radial current balance, shows that a considerable E×B shear, relevant for turbulence suppression, can be generated by orbit losses. In contrast to earlier orbit loss models, no spontaneous bifurcation of the radial electric field E_r is found. However, a bifurcation and a solitary E_r generation are found in simulations with electrode polarization.