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.
- Research Organization:
- Univ. of California, Los Angeles, CA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- FC02-04ER54698; FG02-08ER54984; FG03-86ER53266
- OSTI ID:
- 1354786
- Alternate ID(s):
- OSTI ID: 1252264
- Journal Information:
- Physics of Plasmas, Vol. 23, Issue 5; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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