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Studies of the fast ion confinement in the Large Helical Device by using neutron measurement and integrated codes

Part of: Focus on Fusion

Published online by Cambridge University Press:  17 June 2020

H. Nuga Open the ORCID record for H. Nuga [Opens in a new window] ,
R. Seki Open the ORCID record for R. Seki [Opens in a new window] ,
K. Ogawa Open the ORCID record for K. Ogawa [Opens in a new window] ,
S. Kamio Open the ORCID record for S. Kamio [Opens in a new window] ,
Y. Fujiwara Open the ORCID record for Y. Fujiwara [Opens in a new window] ,
M. Osakabe Open the ORCID record for M. Osakabe [Opens in a new window] ,
M. Isobe Open the ORCID record for M. Isobe [Opens in a new window] ,
T. Nishitani Open the ORCID record for T. Nishitani [Opens in a new window] ,
M. Yokoyama Open the ORCID record for M. Yokoyama [Opens in a new window]  and
LHD Experiment Group
H. Nuga*
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan
R. Seki
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
K. Ogawa
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
S. Kamio
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan
Y. Fujiwara
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan
M. Osakabe
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
M. Isobe
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
T. Nishitani
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan
M. Yokoyama
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
LHD Experiment Group
Affiliation:
National Institute for Fusion Sciences, National Institutes of Natural Sciences, Toki, Japan
*
†Email address for correspondence: nuga.hideo@nifs.ac.jp
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Abstract

The neutral beam (NB) fast ion confinement in the Large Helical Device (LHD) is studied for several full field ($B_{t}\sim 2.75~\text{T}$) magnetic configurations by a combination of neutron measurement and simulations. To investigate the NB fast ion confinement, we have performed a series of short-pulse NB injection experiments. The experiment results are analysed by the integrated code TASK3D-a. From this investigation, the effective particle diffusion coefficients of the tangential and perpendicular NBs are approximately $D^{\text{eff}}\sim 0.1~\text{m}^{2}~\text{s}^{-1}$ and $D^{\text{eff}}\sim 1~\text{m}^{2}~\text{s}^{-1}$ in the standard configuration. It is clarified that the NB fast ion confinement improves when the plasmas are shifted inward. Moreover, it is also found that the simulation, which considers the deuteron dilution effect due to the presence of impurity ions, can describe a neutron emission rate consistent with the measurement.

Keywords

fusion plasmaplasma confinementplasma heating
Type
Research Article
Information
Journal of Plasma Physics , Volume 86 , Issue 3 , June 2020 , 815860306
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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