Micro-tearing mode dominated electron heat transport in DIII-D H-mode pedestal

Nuclear Fushion

article

J. Chen¹  X. Jian²  D.L. Brower¹  S.R. Haskey³  Z. Yan⁴  R. Groebner⁵  H.Q. Wang⁵  T.L. Rhodes¹  F. Laggner³  W. Ding¹  K. Barada¹  S. Banerjee³ 

[1] University of California Los Angeles;University of California San Diego;Princeton Plasma Physics Laboratory, Princeton;University of Wisconsin-Madison;General Atomics

关键词: micro-tearing modes;    magnetic fluctuation;    electron heat transport;    pedestal;   

DOI  :  10.1088/1741-4326/accafb

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

A new, comprehensive set of evidence reveals that Micro-Tearing Modes (MTMs) dominate pedestal electron heat transport in an H-mode experiment in the DIII-D tokamak. The experiment investigates the role of MTMs by scanning pedestal collisionality, a main drive of MTM instability, from 0.43 to 0.84 on the pedestal top. Broadband (150–800 kHz) magnetic and density fluctuations originating from the pedestal gradient region and highly consistent with MTMs are observed, with amplitude increasing during the scan. The higher magnetic fluctuation amplitude correlates with a lower pedestal electron temperature gradient, implying MTMs may regulate the pedestal electron heat transport. The collisionality scan results in profile and transport changes consistent with predicted transport capability of MTMs: (1) experimentally-determined electron heat diffusivity increases ∼40% at the location where the broadband density fluctuations peak; (2) ion heat diffusivity has less increase (<20%); and (3) a locally flattened region in the electron temperature pedestal is observed at high collisionality. A local, linear gyrokinetic simulation finds MTMs as the most unstable mode in the pedestal gradient region. In addition, local, nonlinear simulations suggest MTMs can dominate and drive experimentally-relevant, megawatt-level electron heat flux. This result establishes MTMs as an effective transport mechanism in the H-mode pedestal, in particular at high collisionality.

【 授权许可】

Unknown