Comparison of detachment in Ohmic plasmas with positive and negative triangularity

IF 2.1 2区 物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS Plasma Physics and Controlled Fusion Pub Date : 2024-04-21 DOI:10.1088/1361-6587/ad3c1c
O Février, C K Tsui, G Durr-Legoupil-Nicoud, C Theiler, M Carpita, S Coda, C Colandrea, B P Duval, S Gorno, E Huett, B Linehan, A Perek, L Porte, H Reimerdes, O Sauter, E Tonello, M Zurita, T Bolzonella, F Sciortino, the TCV Team and the EUROfusion Tokamak Exploitation Team
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Abstract

In recent years, negative triangularity (NT) has emerged as a potential high-confinement L-mode reactor solution. In this work, detachment is investigated using core density ramps in lower single null Ohmic L-mode plasmas across a wide range of upper, lower, and average triangularity (the mean of upper and lower triangularity: δ) in the TCV tokamak. It is universally found that detachment is more difficult to access for NT shaping. The outer divertor leg of discharges with could not be cooled to below through core density ramps alone. The behavior of the upstream plasma and geometrical divertor effects (e.g. a reduced connection length with negative lower triangularity) do not fully explain the challenges in detaching NT plasmas. Langmuir probe measurements of the target heat flux widths (λq) were constant to within 30% across an upper triangularity scan, while the spreading factor S was lower by up to 50% for NT, indicating a generally lower integral scrape-off layer width, λint. The line-averaged core density was typically higher for NT discharges for a given fuelling rate, possibly linked to higher particle confinement in NT. Conversely, the divertor neutral pressure and integrated particle fluxes to the targets were typically lower for the same line-averaged density, indicating that NT configurations may be closer to the sheath-limited regime than their PT counterparts, which may explain why NT is more challenging to detach.
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正三角和负三角欧姆等离子体中脱离现象的比较
近年来,负三角形(NT)已成为一种潜在的高稠度 L 型反应堆解决方案。在这项工作中,我们在 TCV 托卡马克中使用下单空欧姆 L 模式等离子体中的堆芯密度斜坡来研究脱落问题,研究范围包括上三角度、下三角度和平均三角度(上三角度和下三角度的平均值:δ)。人们普遍发现,要对 NT 进行整形,分离是比较困难的。仅通过堆芯密度斜坡无法将放电的外侧分流段冷却到下方。上游等离子体的行为和分流器的几何效应(如负下三角的连接长度缩短)并不能完全解释分离 NT 等离子体所面临的挑战。对目标热通量宽度(λq)的朗缪尔探针测量结果在上三角扫描范围内保持稳定,误差在 30% 以内,而对于 NT 来说,扩展因子 S 降低了 50% 之多,这表明整体刮离层宽度 λint 普遍较低。在给定燃料率的情况下,NT 放电的线平均堆芯密度通常较高,这可能与 NT 中较高的粒子约束有关。与此相反,在相同的线均密度下,转发器中性压力和到达目标的综合粒子通量通常较低,这表明与 PT 相比,NT 配置可能更接近鞘限制机制,这也许可以解释为什么 NT 更难脱离。
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来源期刊
Plasma Physics and Controlled Fusion
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.
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