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

Nuclear Fushion

article

T. Kobayashi¹  H. Takahashi¹  K. Nagaoka¹  K. Tanaka¹  R. Seki¹  H. Yamaguchi¹  M. Nakata¹  M. Sasaki⁴  M. Yoshinuma¹  K. Ida¹ 

[1] National Institute for Fusion Science, National Institutes of Natural Sciences;The Graduate University for Advanced Studies;Graduate School of Science, Nagoya University;College of Industrial Technology, Nihon University

关键词: isotope effect;    internal transport barrier;    turbulence;    radial electric field;    stellarators;   

DOI  :  10.1088/1741-4326/ac298f

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

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

【 授权许可】

Unknown