Role of fast-ion transport manipulating safety factor profile in KSTAR early diverting discharges

Kang, J.; Rhee, T.; Kim, J.; Podestà, M.; Bardóczi, L.; Nazikian, R.; Cheng, C. Z.; Kramer, G. J.; Choi, M. J.; Hahn, S. H.; Han, H.; Woo, M. H.; Jhang, H.; Park, J. M.; Kwon, J. M.

doi:10.1088/1741-4326/abb25b

Title: Role of fast-ion transport manipulating safety factor profile in KSTAR early diverting discharges

Journal Article · Tue Oct 13 00:00:00 EDT 2020 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/abb25b· OSTI ID:1814845

^[1]; Rhee, T. ^[1];

^[1];

^[2]; Bardóczi, L. ^[3];

^[2]; Cheng, C. Z. ^[2];

^[2];

^[1];

^[1]; Jhang, H. ^[1]; Park, J. M. ^[4]; Kwon, J. M. ^[1]

National Fusion Research Inst., Daejeon (Korea)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
General Atomics, San Diego, CA (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Magnetohydrodynamics (MHD) activity is analyzed for a particular KSTAR discharge category, the main features of which are a high-$$q_\mathrm{min}$$ and a broad q profile. An interesting finding in this scenario is that a steady-state high-$$q_\mathrm{min}$$ and broad q profile has been constructed even without a strong off-axis current drive scheme. Time traces of magnetics spectrograms and electron cyclotron emission imaging (ECEI) clearly show that Alfvénic type MHD activity appears as a high-$$q_\mathrm{min}$$ and broad q profile is formed. Conversely, this activity disappears as the current profiles evolve toward a low-$$q_\mathrm{min}$$ profile. In this study, the effect of MHD modes and accompanying fast-particle transport on the formation of various current profiles is explored. The frequency patterns of the magnetics spectrograms and ECEI coherence are compared using a NOVA analysis to determine which series of Alfvénic modes are active. Then, the kick-model is applied to potential modes, and used to estimate how much fast-ions are transported and beam driven current profiles are varied. Here, by comparing the reconstructed total current profile from the kinetic EFIT with the beam-driven current profile estimated from the kick model, it is determined how energetic particle transport is responsible for maintaining the safety factor profile and which q profile can provide high β_N operation.

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Research Organization:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: Ministry of Science and ICT

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1814845

Journal Information:: Nuclear Fusion, Vol. 60, Issue 12; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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