Internal transport barrier formation induced by edge perturbation on LHD

摘要

The electron internal transport barrier (ITB) is formed by an edge perturbation induced by a tracer encapsulated solid pellet injection in a net-current free LHD plasma. The ITB trigger by an edge perturbation takes place in the low density regime and the ITB is not accompanied by a significant change in the density. At the onset of the core temperature rise, there is a strong correlation between the heat flux in the central region and the temperature gradient at a distance half of the plasma radius away. A radial temperature profile with a concave curvature abruptly appears in the growing phase of temperature gradient. Turbulence suppression mechanisms via flow and magnetic shears are not sufficient to explain these features.