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Report No.

Characteristics of the first H-mode discharges in KSTAR

Yoon, S. W.*; Ahn, J.-W.*; Jeon, Y. M.*; Suzuki, Takahiro; Hahn, S. H.*; Ko, W. H.*; Lee, K. D.*; Chung, J. I.*; Nam, Y. U.*; Kim, J.*; Hong, S. H.*; Kim, H.-S.*; Kim, W. C.*; Oh, Y. K.*; Kwak, J. G.*; Park, Y. S.*; Sabbagh, S. A.*; Humphreys, D. A.*; Na, Y. S.*; Kim, K. M.*; Yun, G. S.*; Hyatt, A. W.*; Gohil, P.*; Bae, Y. S.*; Yang, H. L.*; Park, H. K.*; Kwon, M.*; Lee, G. S.*; KSTAR Team*

Typical ELMy H-mode discharges have been achieved on the KSTAR tokamak with the combined auxiliary heating of NBI and ECRH. The minimum external heating power required is about 1.1 MW at a line-averaged density higher than 1.4$$times$$10$$^{19}$$ m$$^{-3}$$ and a toroidal field of 2 T. There is a clear indication of the increase of the L-H threshold power at densities lower than $$1.4times 10^{19} {rm m}^{-3}$$. The initial analysis of energy confinement time ($$tau$$$$_{E}$$) predicted that $$tau$$$$_{E}$$ was higher than the prediction of multi-machine scaling laws by a factor 1.4-1.6. However, when the contribution of fast ion confinement to the total energy was taken into account, $$tau$$$$_{E}$$ better agreed with the scaling results. A clear increase of electron and ion temperature in the pedestal was observed in the H-mode phase but the core ion temperature did not change significantly. On the other hand, the toroidal rotation also increased over all radii in the H-mode phase. The measured ELM frequency was from 30-50 Hz and the drop of total energy appeared to be less than 5%. Between large ELM spikes, small/grassy ELMs were also identified when mixed heating of NBI and ECRH was applied.



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Category:Physics, Fluids & Plasmas



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