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Impact of central ECCD on Steady-state hybrid scenario in DIII-D

Author(s): Petty, CC; Nazikian, R; Van Zeeland, MA; Pace, DC; Grierson, BA; et al

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Abstract: © 2015 AIP Publishing LLC. "Steady-state" hybrid plasmas in DIII-D with zero surface loop voltage have been maintained for up to two current relaxation times using 3.4 MW of central electron cyclotron current drive (ECCD). In addition to driving ≈0.2 MA of plasma current, central ECCD leads to significant changes in Alfvén eigenmode (AE) activity and thermal transport. For neutral-beam-only heating, strong AE activity is observed that causes a ∼35% degradation in the neutron rate. With central ECCD this AE activity is suppressed, replaced by a bursty energetic particle mode that appears more benign as the neutron rate is closer to the classical value. The electron thermal diffusivity increases by ≈50% for 2.4 MW of ECCD compared to neutral-beam-only cases. Fortunately, the global thermal confinement factor remains the same (H98y2=1.4) as the higher thermal transport for PEC=2.4 MW hybrids is offset by the decreased fast ion transport resulting from AE suppression.
Publication Date: 10-Dec-2015
Citation: Petty, CC, Nazikian, R, Van Zeeland, MA, Pace, DC, Grierson, BA, Chen, X, Kolemen, E, McKee, GR, Prater, R, Turco, F. (2015). Impact of central ECCD on Steady-state hybrid scenario in DIII-D. AIP Conference Proceedings, 1689 (10.1063/1.4936539
DOI: doi:10.1063/1.4936539
ISSN: 0094-243X
EISSN: 1551-7616
Type of Material: Conference Article
Journal/Proceeding Title: AIP Conference Proceedings
Version: Final published version. This is an open access article.

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