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Author(s):
R. Seki, K. Watanabe, H. Funaba, Y. Suzuki, Y. Matsumoto, K. Hamamatsu, S. Sakakibara and S. Ohdachi
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Title:
Re-entering Fast Ion Effects on NBI Heating Power in High-Beta Plasmas of the Large Helical Device
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Date of publication:
Oct. 17, 2011
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Key words:
re-entering fast ion, high-beta plasma, heating power, Monte-Carlo calculation, large helical device
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Abstract:
We calculate the heating power of the neutral beam injection (NBI) in the <beta> = 4:8% high-beta discharge achieved in the Large Helical Device (LHD). We investigate the difference of the heating efficiency and the heating power profile between with and without the re-entering fast ion effects. When the re-entering fast ion effects are taken into account, the heating efficiency in the co injection of the NBI (co-NBI case) is improved and it is about 1.8 times larger than that without the re-entering effects. In contrast, the heating efficiency with the re-entering effects in the counter injection of the NBI (ctr-NBI case) rarely differs from that without the re-entering ones. We also study the re-entering fast ion effects on the transport properties in the LHD high beta discharges. It is found that the tendency of the thermal conductivities on the beta value is not so much sensitive with and without the re-entering effects. In addition, we investigate the difference in the re-entering fast ion effects caused by the field strength and the magnetic configuration. In the co-NBI case, the re-entering fast ion effects on the heating efficiency increases with the decrease of the field strength. In the contrast, the re-entering fast ion effects in the ctr-NBI case rarely differs by changing the field strength.
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