[Table of Contents]

Plasma and Fusion Research

Volume 9, 3403127 (2014)

Regular Articles

Effect of Impurity Ions on NBI Heating in LHD Plasmas
Hiroyuki YAMAGUCHI and Sadayoshi MURAKAMI
Department of Nuclear Engineering, Kyoto University, Nishikyo, Kyoto 615-8530, Japan
(Received 10 December 2013 / Accepted 17 April 2014 / Published 29 July 2014)


The effect of impurity ions on NBI heating is numerically investigated in LHD plasmas. Helium and carbon are the two impurity species considered in the simulation. Fast-ion birth rates with various impurity fractions are calculated using the HFREYA code, taking into account ionization by the electron and ion impacts, and the charge exchanges with ions. The fast-ion birth rate is found to increase with increasing effective charge of plasma in the tangential injection NBI heating (beam energy: 180 keV) case, whereas the birth rate decreased in the perpendicular injection one (beam energy: 40 keV). The fast-ion slowing down is calculated using the GNET code, considering the Coulomb collisions with electrons, protons, and impurity ions. As the impurity fraction increases, the fast-ion confinement deteriorates because of the enhancement of the pitch-angle scatterings. Also, as the impurity fraction increases, the heat deposition per ion increases in the tangential injection NBI case and decreases in the perpendicular one.


NBI heating, impurity, Large Helical Device, GNET

DOI: 10.1585/pfr.9.3403127


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This paper may be cited as follows:

Hiroyuki YAMAGUCHI and Sadayoshi MURAKAMI, Plasma Fusion Res. 9, 3403127 (2014).