Plasma and Fusion Research
Online ISSN : 1880-6821
ISSN-L : 1880-6821
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Measurements of Plasma Termination in ICRF Heated Long Pulse Discharges with Fast Framing Cameras in the Large Helical Device
Mamoru SHOJIHiroshi KASAHARAHirohiko TANAKATetsuo SEKIKenji SAITOShuji KAMIORyosuke SEKITakashi MUTOHMasayuki TOKITANIShigeru MORITAMotoshi GOTOTetsutaro OISHIEduardo DE LA CALCarlos HIDALGOHiroshi YAMADAthe LHD Experiment Group
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2015 Volume 10 Pages 3402040

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Abstract

The termination process of long pulse plasma discharges in the Large Helical Device (LHD) have been observed with fast framing cameras, which shows that the reason for the termination of the discharged has been changed with increased plasma heating power, improvements of plasma heating systems and change of the divertor configuration, etc. For long pulse discharges in FYs2010-2012, the main reason triggering the plasma termination was reduction of ICRF heating power with rise of iron ion emission due to electric breakdown in an ICRF antenna. In the experimental campaign in FY2013, the duration time of ICRF heated long pulse plasma discharges has been extended to about 48 minutes with a plasma heating power of ∼1.2 MW and a line-averaged electron density of ∼1.2×1019 m−3. The termination of the discharges was triggered by release of large amounts of carbon dusts from closed divertor regions, indicating that the control of dust formation in the divertor regions is indispensable for extending the duration time of long pulse discharges.

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© 2015 by The Japan Society of Plasma Science and Nuclear Fusion Research
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