Characterization of the ELM-free negative triangularity edge on DIII-D

IF 2.1 2区物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS

Plasma Physics and Controlled Fusion Pub Date : 2024-09-05 DOI:10.1088/1361-6587/ad6a83

A O Nelson, L Schmitz, T Cote, J F Parisi, S Stewart, C Paz-Soldan, K E Thome, M E Austin, F Scotti, J L Barr, A Hyatt, N Leuthold, A Marinoni, T Neiser, T Osborne, N Richner, A S Welander, W P Wehner, R Wilcox, T M Wilks, J Yang, the DIII-D Team3

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引用次数: 0

Abstract

Tokamak plasmas with strong negative triangularity (NT) shaping typically exhibit fundamentally different edge behavior than conventional L-mode or H-mode plasmas. On DIII-D, every plasma with sufficiently negative triangularity (

δ<δcrit≃−0.12

) is found to be inherently free of edge localized modes (ELMs), even at injected powers well above the predicted L-H power threshold. It is also possible to access an ELM-free state at weaker average triangularities, provided that at least one of the two x-points is still sufficiently negative. Access to the ELM-free NT scenario is found to coincide with the closure of the second stability region for infinite-n ballooning modes, suggesting that ballooning stability may play a role in limiting the accessible pressure gradient in NT plasmas. Despite this, NT plasmas are able to support small pedestals and are typically characterized by an enhancement of edge pressure gradients beyond those found in traditional L-mode plasmas. Furthermore, the pressure gradient inside of this small pedestal is unusually steep, allowing access to high core performance that is competitive with other ELM-free regimes previously achieved on DIII-D. Since ELM-free operation in NT is linked directly to the magnetic geometry, NT fusion pilot plants are predicted to maintain advantageous edge conditions even in burning plasma regimes, potentially eliminating reactor core-integration issues caused by ELMs.

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DIII-D 上无 ELM 负三角形边缘的特征

与传统的 L 模式或 H 模式等离子体相比，具有强负三角形（NT）形状的托卡马克等离子体通常会表现出根本不同的边缘行为。在 DIII-D 上，我们发现每一个具有足够负三角形（δ<δcrit≃-0.12）的等离子体本质上都不存在边缘局部模式（ELM），即使注入功率远高于预测的 L-H 功率阈值。只要两个 x 点中至少有一个仍然足够负，也有可能在较弱的平均三角形下进入无 ELM 状态。进入无 ELM 的 NT 情景与无限 n 气球模式第二个稳定区域的关闭相吻合，这表明气球稳定性可能在限制 NT 等离子体中可获得的压力梯度方面发挥作用。尽管如此，NT 等离子体仍能支持小基座，其典型特征是边缘压力梯度的增强超过了传统 L 模式等离子体。此外，这种小基座内部的压力梯度异常陡峭，因此可以获得与之前在 DIII-D 上实现的其他无 ELM 状态相媲美的高核心性能。由于 NT 中的无 ELM 运行与磁几何学直接相关，因此预计 NT 核聚变试验装置即使在燃烧等离子体状态下也能保持有利的边缘条件，从而有可能消除 ELM 导致的反应堆堆芯集成问题。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Plasma Physics and Controlled Fusion 物理-物理：核物理

CiteScore

4.50

自引率

13.60%

发文量

224

审稿时长

4.5 months

期刊介绍： Plasma Physics and Controlled Fusion covers all aspects of the physics of hot, highly ionised plasmas. This includes results of current experimental and theoretical research on all aspects of the physics of high-temperature plasmas and of controlled nuclear fusion, including the basic phenomena in highly-ionised gases in the laboratory, in the ionosphere and in space, in magnetic-confinement and inertial-confinement fusion as well as related diagnostic methods. Papers with a technological emphasis, for example in such topics as plasma control, fusion technology and diagnostics, are welcomed when the plasma physics is an integral part of the paper or when the technology is unique to plasma applications or new to the field of plasma physics. Papers on dusty plasma physics are welcome when there is a clear relevance to fusion.