Recently, a European transport project has been carried out among several fusion devices for studying the possible link between the mean radial electric field (Er), long-range correlation (LRC) and edge bifurcations in fusion plasmas. The main results reported in this paper include: (i) the discovery of low-frequency LRCs in potential fluctuations which are amplified during the development of edge mean Er using electrode biasing and during the spontaneous development of edge sheared flows in stellarators and tokamaks. Evidence of nonlocal energy transfer and the geodesic acoustic mode modulation on local turbulent transport have also been observed. The observed LRCs are consistent with the theory of zonal flows described by a 'predator–prey' model. The results point to a significant link between the LRC and transport bifurcation. (ii) Comparative studies in tokamaks, stellarators and reversed field pinches have revealed significant differences in the level of the LRC. Whereas the LRCs are clearly observed in tokamaks and stellarators, no clear signature of LRCs was seen in the RFX-mod reversed field pinch experiments. These results suggest the possible influence of magnetic perturbations on the LRC, in agreement with recent observations in the resonant magnetic perturbation experiments at the TEXTOR tokamak. (iii) The degree of the LRCs is strongly reduced on approaching the plasma density-limit in tokamaks and stellarators, suggesting the possible role of collisionality or/and the impact of mean Er × B flow shear on zonal flows.
最近，在欧洲的一个联合运输项目中，针对多个聚变装置，研究了等离子体边缘平均径向电场（Er）、长程相关（LRC）与边缘分叉之间的可能联系。本文报告的主要结果包括：（i）在多个仿星器和托卡马克装置中，通过电极偏压产生边缘平均Er以及自发产生边缘剪切流的过程中，观测到电位涨落中的低频LRC被放大。同时，也观测到了非局域能量输运以及测地声模对局域湍流输运的调制。观测到的LRC与描述带状流的“捕食者-猎物”模型理论一致。这些结果表明，LRC与输运分叉之间存在显著联系。（ii）在托卡马克、仿星器和反场箍缩装置中的比较研究表明，LRC的水平存在显著差异。在托卡马克和仿星器中清晰观测到LRC，而在RFX-mod反场箍缩装置实验中则未观察到明显的LRC特征。这些结果暗示了磁扰动可能对LRC产生影响，这与TEXTOR托卡马克共振磁扰动实验中的最新观测结果相符。（iii）在托卡马克和仿星器中，当接近等离子体密度极限时，LRC的程度显著降低，这表明碰撞率可能发挥作用，或者平均Er×B剪切流对带状流的影响是关键因素。