학술논문
The role of shear flow collapse and enhanced turbulence spreading in edge cooling approaching the density limit
Document Type
article
Author
Long, Ting; Diamond, PH; Ke, Rui; Chen, Zhipeng; Xu, Xin; Tian, Wenjing; Hong, Rongjie; Cao, Mingyun; Liu, Yanmin; Xu, Min; Wang, Lu; Yang, Zhoujun; Yuan, Jinbang; Zhou, Yongkang; Yan, Qinghao; Yang, Qinghu; Shen, Chengshuo; Nie, Lin; Wang, Zhanhui; Hao, Guangzhou; Wang, Nengchao; Chen, Zhongyong; Li, Jiquan; Chen, Wei; Zhong, Wulyu
Source
Nuclear Fusion. 64(6)
Subject
Language
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.