Suppression of toroidal Alfvén eigenmodes by the electron cyclotron current drive in KSTAR plasmas

Kim, Junghee; Kang, Jisung; Rhee, Tongnyeol; Jo, J.; Han, Hyunsun; Podestà, Mario; Lee, Jaehyun H.; Lee, S.; Bak, Jun Gyo; Choi, Minjun J.; Nazikian, Raffi; Jhang, Hogun; Ko, Jinseok; Joung, M.; Jeon, YoungMu; Na, Yong-Su; Shinohara, Kouji; Cheng, C. Z.

doi:10.1088/1741-4326/ac3e39

Title: Suppression of toroidal Alfvén eigenmodes by the electron cyclotron current drive in KSTAR plasmas

Journal Article · 03 January 2022 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ac3e39 · OSTI ID:1856187

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Korea Institute of Fusion Energy, Daejeon (Korea, Republic of)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Seoul National Univ. (Korea, Republic of)
Univ. of Tokyo, Kashiwa (Japan)

Advanced operation scenarios such as high poloidal beta (β_P) or high q_min are promising concepts to achieve the steady-state high-performance fusion plasmas. However, those scenarios are prone to substantial Alfvénic activity, causing fast-ion transport and losses. Recent experiments with the advanced operation scenario on KSTAR tokamak have shown that the electron cyclotron current drive (ECCD) is able to mitigate and suppress the beam-ion driven toroidal Alfvén eigenmodes (TAEs) for over several tens of global energy confinement time. Co-current directional intermediate off-axis ECCD lowers the central safety factor slightly and tilts the central q-profile shape so that the continuum damping in the core region increases. Besides, the rise of central plasma pressure and increased thermal-ion Landau damping contribute to TAE stabilization. While the TAEs are suppressed, neutron emission rate and total stored energy increase by approximately 45% and 25%, respectively. Fast-ion transport estimated by TRANSP calculations approaches the classical level during the TAE suppression period. Substantial reduction in fast-ion loss and neutron deficit is also observed. Subsequently, enhancement of fast-ion confinement by suppressing the TAEs leads to an increase of non-inductive current fraction and will benefit the sustainment of the long-pulse high-performance discharges.

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

Sponsoring Organization:: USDOE; Korea Institute of Fusion Energy (KFE)

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1856187

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 2 Vol. 62; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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