Experimental studies of the dynamics of shear flow and turbulence spreading at the edge of tokamak plasmas are reported. Scans of line-averaged density and plasma current are carried out while approaching the Greenwald density limit on the J-TEXT tokamak. In all scans, when the Greenwald fraction increases, a common feature of enhanced turbulence spreading and edge cooling is found. The result suggests that turbulence spreading is a good indicator of edge cooling, indeed better than turbulent particle transport is. The normalized turbulence spreading power increases significantly when the normalized shearing rate decreases. This indicates that turbulence spreading becomes prominent when the shearing rate is weaker than the turbulence scattering rate. The asymmetry between positive/negative (blobs/holes) spreading events, turbulence spreading power and shear flow are discussed. These results elucidate the important effects of interaction between shear flow and turbulence spreading on plasma edge cooling.
Long, Ting, et al. "The role of shear flow collapse and enhanced turbulence spreading in edge cooling approaching the density limit." Nuclear Fusion, vol. 64, no. 6, Apr. 2024. https://doi.org/10.1088/1741-4326/ad3e15
Long, Ting, Diamond, P. H., Ke, Rui, et al., "The role of shear flow collapse and enhanced turbulence spreading in edge cooling approaching the density limit," Nuclear Fusion 64, no. 6 (2024), https://doi.org/10.1088/1741-4326/ad3e15
@article{osti_2341353,
author = {Long, Ting and Diamond, P. H. and Ke, Rui and Chen, Zhipeng and Xu, Xin and Tian, Wenjing and Hong, Rongjie and Cao, Mingyun and Liu, Yanmin and Xu, Min and others},
title = {The role of shear flow collapse and enhanced turbulence spreading in edge cooling approaching the density limit},
annote = {Abstract Experimental studies of the dynamics of shear flow and turbulence spreading at the edge of tokamak plasmas are reported. Scans of line-averaged density and plasma current are carried out while approaching the Greenwald density limit on the J-TEXT tokamak. In all scans, when the Greenwald fraction f G = n ¯ / n G = n ¯ / ( I p / π a 2 ) increases, a common feature of enhanced turbulence spreading and edge cooling is found. The result suggests that turbulence spreading is a good indicator of edge cooling, indeed better than turbulent particle transport is. The normalized turbulence spreading power increases significantly when the normalized E × B shearing rate decreases. This indicates that turbulence spreading becomes prominent when the shearing rate is weaker than the turbulence scattering rate. The asymmetry between positive/negative (blobs/holes) spreading events, turbulence spreading power and shear flow are discussed. These results elucidate the important effects of interaction between shear flow and turbulence spreading on plasma edge cooling. },
doi = {10.1088/1741-4326/ad3e15},
url = {https://www.osti.gov/biblio/2341353},
journal = {Nuclear Fusion},
issn = {ISSN 0029-5515},
number = {6},
volume = {64},
place = {IAEA},
publisher = {IOP Publishing},
year = {2024},
month = {04}}
Univ. of California, San Diego, CA (United States)
Sponsoring Organization:
Engineering and Physical Sciences Research Council (EPSRC); Ministry of Science and Technology, China; National Natural Science Foundation of China (NSFC); USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 381, Issue 2242https://doi.org/10.1098/rsta.2021.0227