Characterization of isotope effect on ion internal transport barrier and its parameter dependence in the Large Helical Device

Abstract In this paper, the background physics of isotope effects in ion internal transport barrier (ITB) are discussed detail. An heuristic criterion for ITB strength is defined based on nonlinear dependence thermal diffusivity local temperature L-mode phase. Comparing deuterium plasmas and hydrogen plasmas, two clarified: stronger ITBs formed an concomitant edge confinement degradation plasmas. Principal component analysis reveals that becomes strong when a high input power normalized by line averaged electron density applied profile peaked. A gyrokinetic simulation suggests determined gradient driven turbulence, while way saturates unknown. turbulence behavior, branch transition observed, where increasing trend amplitude against flipped to decreasing across formation. The radial electric field structure measured charge exchange recombination spectroscopy system. It found shear plays minor role determining strength.