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Heat transport analysis of the improved confinement discharge with LHW in the HT-7 tokamak

Published online by Cambridge University Press:  15 December 2009

X. M. ZHANG ,
X. SHEN ,
B. N. WAN ,
Z. W. WU  and
J. FU
X. M. ZHANG
Affiliation:
Department of Physics, East China University of Science and Technology, Shanghai 200237, China (zhangxm@ecust.edu.cn, zhangxm25@sina.com.cn)
X. SHEN
Affiliation:
Department of Physics, East China University of Science and Technology, Shanghai 200237, China (zhangxm@ecust.edu.cn, zhangxm25@sina.com.cn)
B. N. WAN
Affiliation:
Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, China
Z. W. WU
Affiliation:
Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, China
J. FU
Affiliation:
Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei 230031, China
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Abstract

In the HT-7 tokamak, heat transport analysis is carried out for the lower hybrid current drive (LHCD) experiments. Electrons and ions are coupled and good confinement can be obtained by properly optimizating LHCD and plasma parameters. Under the conditions that the plasma current is about 220 kA, the lower hybrid wave (LHW) power is about 300 kW and the central line-averaged density is about 1.5×1013 cm−3, lower hybrid wave power deposition is off-axis. Local transport analysis illustrated that both electron and ion thermal diffusivities are decreased during the LHW phase, and the electron internal transport barriers (eITBs) are formed while been accompanied by the ion internal transport barriers (iITBs) during LHW phase. Ions are heated by electron-ion collision in the region of the barriers although the ohmic power and the LHW power were absorbed by the electrons. Both electron temperature and ion temperature are increased during the LHW phase, and in the confinement region, the electron-to-ion temperature ratio, Te/Ti varies from 2.0 ~ 2.5 during OH phase to 1.3 ~ 1.6 during LHW injected into the plasma, which shows that electron confinement is not degraded by the electron–ion collisions meanwhile ions are also confined. The energy confinement is increased from 13 ms to 25 ms due to the formation of electron and ion internal transport barries after the LHW is injected into the plasma. LHW driven current and bootstrap current contribute to 60% of the total current.

Type
Papers
Information
Journal of Plasma Physics , Volume 76 , Issue 2 , April 2010 , pp. 229 - 237
Copyright
Copyright © Cambridge University Press 2009

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