Particle Transport of LHD

Particle confinement processes are studied in detail on the Large Helical Device (LHD). Diffusion coefficients (D) and convection velocities (V) are estimated from density modulation experiments. The magnetic configuration and collisionality are widely scanned in order to investigate parameter depen...

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Bibliographic Details
Published in:Fusion science and technology 2010-08, Vol.58 (1), p.70-90
Main Authors: Tanaka, K., Kawahata, K., Tokuzawa, T., Akiyama, T., Yokoyama, M., Shoji, M., Michael, C. A., Vyacheslavov, L. N., Murakami, S., Wakasa, A., Mishchenko, A., Muraoka, K., Okajima, S., Takenaga, H.
Format: Article
Language:English
Subjects:
Confinement
Convection
Density
Devices
Diffusion
Diffusion coefficient
Electron temperature
Fluid dynamics
Fluid flow
Heating
Helical
Linkages
Modulation
Neutral beams
Ripples
Transport
Turbulence
Turbulent flow
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Summary:Particle confinement processes are studied in detail on the Large Helical Device (LHD). Diffusion coefficients (D) and convection velocities (V) are estimated from density modulation experiments. The magnetic configuration and collisionality are widely scanned in order to investigate parameter dependences of D and V. To study the effect of the magnetic configuration, magnetic axis positions (R ax ) are scanned from 3.5 to 3.9 m. This scan changes the magnetic ripples quite significantly, enabling the effects of neoclassical properties on measured values to be widely elucidated. Dependences of electron temperature (T e ) and helically trapped normalized collisionality are examined using the heating power scan of neutral beam injection. It was found that generally larger (or smaller) contributions of neoclassical transport in the core region, where normalized position ρ < 0.7, resulted in more hollow (or peaked) density profiles. The larger neoclassical contribution was found to be situated at a more outwardly shifted R ax for the same T e and for higher T e or lower ν h * at each R ax . However, it is to be noted that R ax = 3.5 m shows different characteristics from these trends, that is, a more peaked density profile at higher T e or lower ν h *. The edge (ρ > 0.7) diffusion and convection are dominated by anomalous processes. Measured edge turbulence shows a possible linkage.
ISSN:1536-1055
1943-7641
DOI:10.13182/FST10-A10795