Experimental study of the SOL blob spatio-temporal characteristics
 in HL-2A tokamak

doi:10.16568/j.0254-6086.202403014

Abstract

Abstract: The spectral characteristics of the scrape-off layer (SOL) electrostatic fluctuations and blob dynamics have been studied by using two Langmuir probe arrays toroidally separated by 2100mm in HL-2A tokamak. The experimental results demonstrated that the fluctuation along the magnetic field line has the significant toroidal long-range correlation and the estimated parallel wavenumber is almost zero. These characteristics are well consistent with the theoretically predicated interchange instability. An E×B shear layer close to 1.0cm width forms just outside the LCFS during the ECRH, which has the ability to stretch the passing blobs. Conditional average analysis shows the potential difference in one blob increases by up to 40%~60% in ECRH, compared to that in Ohmically-heated plasma, which is much larger than the variation of blob poloidal size (20%~30%). This experimental finding presented here reveals that the increased internal potential differenceis the main cause for driving the blobs to move outward quickly. Therefore, this study provides an alternative interpretation for the additionally intermittent transport observed in ECRH and could help understand the behind physics on blob radial velocity scaling and find suitable control methods for suppression of the blob convective transport in future.

Key words: SOL, blob dynamics, toroidal long-range correlation, E×B shear flow, Langmuir probe

摘要： 在 HL-2A 装置上，采用环向相距 2100mm 的组合探针阵列研究了刮削层涨落谱特征和阵发性丝状结构(blob) 动力学过程。实验结果表明，沿磁力线方向静电涨落具有强的环向长程相关性，平行波数接近 0，符合交换模的特征。电子回旋共振加热(ECRH)期间，在最后闭合磁面外侧形成径向宽度约 1.0cm 的 E×B 剪切层，它对经过该区域的 blob 具有一定的拉伸作用。条件平均方法分析指出，ECRH 期间相比于欧姆加热条件下 blob 极向尺寸仅增加了 20%~30%，但 blob 内部电势差增大了约 40%~60%，暗示了 blob 内部电势差增加是导致 blob 径向速度增加的主要原因。这些实验结果为 ECRH 期间观察到 blob 阵发性输运的增加提供了一种解释，对理解 blob 径向速度定标律以及控制 blob 对流输运具有重要的意义。

关键词: 刮削层, 丝状结构动力学, 环向长程相关, E×B 剪切流, 朗缪尔探针

CLC Number:

TL65+ 6

ZHU You-jing , CHENG Jun , YAN Long-wen , WANG Wei-ce , HUANG Zhi-hui , WU Na , XU Yu-hong , SHI Zhong-bing , JI Xiao-quan , ZHONG Wu-lü , XU Min. Experimental study of the SOL blob spatio-temporal characteristics in HL-2A tokamak [J]. Nuclear Fusion and Plasma Physics, 2024, 44(3): 334-342.

朱有敬, 程钧, 严龙文, 王威策, 黄治辉, 吴娜, 许宇鸿, 石中兵, 季小全, 钟武律, 许敏 . HL-2A 装置上刮削层丝状结构时空特征的实验研究[J]. 核工业西南物理研究院, 2024, 44(3): 334-342.

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Experimental study of the SOL blob spatio-temporal characteristics in HL-2A tokamak

HL-2A 装置上刮削层丝状结构时空特征的实验研究

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