Dependence of upstream SOL density shoulder on divertor neutral pressure observed in L-mode and H-mode plasmas in the EAST superconducting tokamak
Dependence of upstream SOL density shoulder on divertor neutral pressure observed in L-mode and H-mode plasmas in the EAST superconducting tokamak
复制标题
上游 SOL 密度肩对 EAST 超导托卡马克 L 模式和 H 模式等离子体中观察到的偏滤器中性压力的依赖性
DOI：
10.1088/1741-4326/abfe47
复制
发表时间：
2021-05
期刊：
影响因子：
3.3
通讯作者：
Liu J. B.
中科院分区：
文献类型：
--
作者：
Yan N.;Chen L.;Xu G. S.;Wu X. Q.;Liu S. C.;Wang Y. F.;Meng L. Y.;Hu G. H.;Zhao N.;Lan H.;Naulin V.;Nielsen A. H.;Juul Rasmussen J.;Li K. D.;Wang L.;Yang Q. Q.;Li M. H.;Ye Y.;Ding R.;Tao Y. Q.;Qian Y. Z.;Hou J. L.;Liu X.;Liu J. B.
在EAST超导托卡马克装置上，研究了低约束模（L模）和高约束模（H模）等离子体中刮削层（SOL）的上游密度分布。当在下偏滤器测量的中性压力超过L模等离子体中2 × 10−2 Pa的阈值时，在上单零组态中的近SOL区域形成弱密度肩。当中性压力低于这个阈值时，弱密度肩不存在，并且与SOL参数不稳定性相关的低混合波的边带减少。使用氘-氘播种的主动分离控制表明，只要中性压力高于阈值，弱密度肩可以在外偏滤器分离开始之前形成。此外，在偏滤器分离过程中没有观察到显著的肩部扩张，这表明偏滤器分离不是密度肩部形成或生长的必要条件。通过将偏滤器下部的中性压力增加一个数量级，观察到弱肩扩展到远SOL并到达限制器的前缘。在L模式放电的结果确定的中性压力在较低的偏滤器作为一个主要因素的形成SOL密度肩在上单零放电。对于I型ELMy H模等离子体，当下偏滤器中的中性压力超过4 × 10−2 Pa的阈值时，在ELM间阶段检测到类似的密度肩。另一方面，肩是缺席时，偏滤器中性压力低于这个阈值，即使进行等离子体放电具有较高的芯线平均密度和偏滤器碰撞。这与L模式等离子体中的观察结果一致。因此，工作气体的中性粒子电离被认为在EAST托卡马克中SOL密度肩的形成过程中起着关键作用。
Upstream density profiles in the scrape-off layer (SOL) have been examined in low-confinement mode (L-mode) and high-confinement mode (H-mode) plasmas in the EAST superconducting tokamak. A weak density shoulder forms in the near SOL region in upper single-null configurations when the neutral pressure measured at the lower divertor exceeds a threshold value of 2 × 10−2 Pa in L-mode plasmas. When the neutral pressure is below this threshold, the weak density shoulder is absent and the sidebands of the lower hybrid waves associated with SOL parametric instabilities are reduced. Active detachment control with neon–deuterium seeding demonstrate that the weak density shoulder can form before the onset of the outer divertor detachment as long as the neutral pressure is above the threshold. Furthermore, no remarkable expansion of a shoulder is observed during divertor detachment, suggesting that divertor detachment is not a necessary condition for the formation or growth of a density shoulder. Through the increase in neutral pressure in the lower divertor by an order of magnitude, the weak shoulder was observed to expand into the far SOL and reach the leading edge of the limiter. The results in L-mode discharges identified the neutral pressure in the lower divertor as a primary factor for the formation of an SOL density shoulder in the upper single-null discharges. For the type-I ELMy H-mode plasmas, a similar density shoulder was detected during the inter-ELM phase when the neutral pressure in the lower divertor exceeded a threshold value of 4 × 10−2 Pa. On the other hand, the shoulder was absent when the divertor neutral pressure went below this threshold even though the plasma discharge was conducted with a higher core line-averaged density and divertor collisionality. This is consistent with the observations in L-mode plasmas. The neutral particle ionization of the working gas is thus believed to play a key role during the formation of the SOL density shoulder in the EAST tokamak.
影响因子：
3.3
作者：
Shimada, M.;Campbell, D. J.;Sipps, A. C. C.
通讯作者：
Sipps, A. C. C.
影响因子：
3.3
作者：
K. Ikeda
通讯作者：
K. Ikeda