Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device

DONG Chunfeng (董春凤); Shigeru MORITA; Motoshi GOTO; WANG Erhui (王二辉); Gen MOTOJIAMA Izumi MURAKAMI; Ryuichi SAKAMOTO; Norimasa YAMAMOTO

doi:10.1088/1009-0630/15/3/08

Plasma Science and Technology > 2013 > 15(3): 230-234. > DOI: 10.1088/1009-0630/15/3/08

DONG Chunfeng (董春凤), Shigeru MORITA, Motoshi GOTO, WANG Erhui (王二辉), Gen MOTOJIAMA Izumi MURAKAMI, Ryuichi SAKAMOTO, Norimasa YAMAMOTO. Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device[J]. Plasma Science and Technology, 2013, 15(3): 230-234. DOI: 10.1088/1009-0630/15/3/08

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Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device

1 National Institute for Fusion Science, Toki 509-5292, Gifu, Japan 2 Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan 3 Center of Applied Superconductivity & Sustainable Energy Research, Chubu University, Kasugai 487-8501, Aichi, Japan

Funds: support by LHD project (NIFS11ULPP010) and partly supported by the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics

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Received Date: January 09, 2012

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Abstract

Abstract

Impurity accumulation is studied for neutral beam-heated discharges after hydrogen multi-pellet injection in Large Helical Device (LHD). Iron density profiles are derived from radial profiles of EUV line emissions of FeXV-XXIV with the help of the collisional-radiative model. A peaked density profile of Fe²³⁺ is simulated by using one-dimensional impurity transport code. The result indicates a large inward velocity of -6 m/s at the impurity accumulation phase. However, the discharge is not entirely affected by the impurity accumulation, since the concentration of iron impurity, estimated to be 3.3x10^-5 to the electron density, is considerably small. On the other hand, a flat profile is observed for the carbon density of C⁶⁺, which is derived from the Z_eff profile, indicating a small inward velocity of -1 m/s. These results suggest atomic number dependence in the impurity accumulation of LHD, which is similar to the tokamak result.
- impurity accumulation,
- EUV spectrometer,
- inward velocity

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