Density scaling on n  =  1 error field penetration in ohmically heated discharges in EAST. (29th March 2018)

• Record Type: Journal Article
• Authors: Wang, Hui-Hui; Sun, You-Wen; Shi, Tong-Hui; Zang, Qing; Liu, Yue-Qiang; Yang, Xu; Gu, Shuai; He, Kai-Yang; Gu, Xiang; Qian, Jin-Ping; Shen, Biao; Luo, Zheng-Ping; Chu, Nan; Jia, Man-Ni; Sheng, Zhi-Cai; Liu, Hai-Qing; Gong, Xian-Zu; Wan, Bao-Nian
• Other Names: collab.
• Is Part Of: Nuclear fusion. Volume 58:Number 5(2018:May)
• Publication Date: 2018-03-29
• Subjects: error field -- density scaling -- theoretical analysis -- EAST; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aab5c0
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Density scaling of error field penetration in EAST is investigated with different n = 1 magnetic perturbation coil configurations in ohmically heated discharges. The density scalings of error field penetration thresholds under two magnetic perturbation spectra are b r ∝ n e 0.5 and b r ∝ n e 0.6, where b r is the error field and n e is the line averaged electron density. One difficulty in understanding the density scaling is that key parameters other than density in determining the field penetration process may also be changed when the plasma density changes. Therefore, they should be determined from experiments. The estimated theoretical analysis ( b r ∝ n e 0.54 in lower density region and b r ∝ n e 0.40 in higher density region), using the density dependence of viscosity diffusion time, electron temperature and mode frequency measured from the experiments, is consistent with the observed scaling. One of the key points to reproduce the observed scaling in EAST is that the viscosity diffusion time estimated from energy confinement time is almost constant. It means that the plasma confinement lies in saturation ohmic confinement regime rather than the linear Neo-Alcator regime causing weak density dependence in the previous theoretical studies.