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Title: Non-perturbative measurement of cross-field thermal diffusivity reduction at the O-point of 2/1 neoclassical tearing mode islands in the DIII-D tokamak

Neoclassical Tearing Modes (NTMs) often lead to the decrease of plasma performance and can lead to disruptions, which makes them a major impediment in the development of operating scenarios in present toroidal fusion devices. Recent gyrokinetic simulations predict a decrease of plasma turbulence and cross- eld transport at the O-point of the islands, which in turn affects the NTM dynamics. In this paper a heat transport model of magnetic islands employing spatially non-uniform cross-field thermal diffusivity (χ$$\perp$$) is presented. This model is used to derive χ$$\perp$$ at the O-point from electron temperature data measured across 2/1 NTM islands in DIII-D. It was found that χ$$\perp$$ at the O-point is 1 to 2 orders of magnitude smaller than the background plasma transport, in qualitative agreement with gyrokinetic predictions. As the anomalously large values of χ$$\perp$$ are often attributed to turbulence driven transport, the reduction of the O-point χ$$\perp$$ is consistent with turbulence reduction found in recent experiments. Lastly, the implication of reduced χ$$\perp$$ at the O-point on NTM dynamics was investigated using the modi ed Rutherford equation that predicts a significant effect of reduced χ$$\perp$$ at the O-point on NTM saturation.
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  1. Univ. of California, Los Angeles, CA (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
FC02-04ER54698; FG02-08ER54984; FG03-86ER53266
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 5; Journal ID: ISSN 1070-664X
American Institute of Physics (AIP)
Research Org:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ntm; tearing; magnetic; island; mhd; transport; turbulence; modeling; experiment; tokamak