@article{oai:nifs-repository.repo.nii.ac.jp:00010802,
 author = {NAGAOKA,  Kenichi and NAGAOKA, Ken-ichi and TAKAHASHI,  Hiromi and Nakata, Motoki and SATAKE,  Shinsuke and TANAKA,  Kenji and Mukai,  Kiyofumi and YOKOYAMA,  Masayuki and NAKANO,  Haruhisa and MURAKAMI,  Sadayoshi and IDA,  Katsumi and YOSHINUMA,  Mikiro and YOSHINUMA,  Mikirou and OHDACHI,  Satoshi and Bando, T. and NUNAMI,  Masanori and SEKI,  Ryosuke and Yamaguchi, Hiroyuki and OSAKABE,  Masaki and MORISAKI,  Tomohiko and LHD, Experiment Group},
 issue = {10},
 journal = {Nuclear Fusion},
 month = {Aug},
 note = {0000-0002-5892-6047, A remarkable extension of the high-ion-temperature (high-Ti) regime was obtained in deuterium plasma experiments in the Large Helical Device. In order to clarify transport characteristics in the ion internal transport barrier (ITB) formation with an isotope effect, a dataset of pure deuterium (nD/ne  >  0.8) and pure hydrogen (nH/ne  >  0.8) plasmas in the high-Ti regime were analyzed, and two mechanisms of transport improvement were characterized. A significant reduction of ion heat transport in the core of both deuterium and hydrogen plasmas was observed, indicating ion ITB formation. The dependence of the ion heat diffusivity on temperature ratio (Te/Ti) and normalized Ti-gradient (R/LTi  =  −(R/Ti)(dTi/dr)) was investigated in the core region, in which gyrokinetic simulations with the GKV code predict the destabilization of ion temperature gradient (ITG) modes. The Te/Ti dependence shows ITG-like property, while a significant deviation from the ITG-like property is found in the R/ dependence, indicating suppression of the ITG mode in the large R/ regime and resultant ion ITB formation. In the comparison between deuterium plasma and hydrogen plasma, the lower transport in the deuterium plasma is observed in both ion and electron heat diffusivities, indicating a significant isotope effect. It was found with the nonlinear turbulent transport simulation with GKV that the zonal flow enhancement contributes to the ITG suppression in the deuterium plasma.},
 title = {Transport characteristics of deuterium and hydrogen plasmas with ion internal transport barrier in the Large Helical Device},
 volume = {59},
 year = {2019}
}