An improved understanding of the roles of atomic processes and power balance in divertor target ion current loss during detachment-猫眼课题宝

DOI：

10.1088/1741-4326/ab4251

发表时间：

2018-10

期刊：

Nuclear Fusion

影响因子：

3.3

通讯作者：

中科院分区：

物理与天体物理1区

文献类型：

作者：

Kevin Verhaegh;B. Lipschultz;B. Duval;O. F'evrier;A. Fil;C. Theiler;M. Wensing;C. Bowman;D. Gahle;J. Harrison;B. Labit;C. Marini;R. Maurizio;H. D. Oliveira;H. Reimerdes;U. Sheikh;C. Tsui;N. Vianello;W. Vijvers;The Tcv Team;The EUROfusion MST1 Team

为了将磁聚变反应堆中的热负荷和侵蚀降低到可接受的水平，需要分流器剥离过程，即流向分流器表面的热量和颗粒通量大大减少。本文在TCV托卡马克上，通过对各种导流汇和源的位置、大小和作用的表征，包括对粒子和功率平衡的完整分析，实验探讨了导致总导流流（It）或“翻转”减小的物理现象。通过新的光谱技术，首次测量了分流器离子化和氢辐射沿分流器腿的剖面。在TCV等离子体条件下的一个范围内（等离子体电流和电子密度，有/没有杂质播种），It翻转归因于导流源的下降；在剥离过程中，复合仍然很小或可以忽略不计。离子源的减少是由可用于电离的功率（Precl）的减少和每次电离所需的能量（Eion）的同时增加所驱动的：这种可用于电离源的功率的影响通常被描述为“功率缺乏”（或“功率限制”）。实验发现（与解析模型预测一致）剥离阈值为~Precl/ ition ~ 2，对应于目标电子温度Tt ~ Eion/γ，其中γ为鞘层透射系数。降低目标离子电流所需的目标压力降低是由体积动量损失和上游压力损失共同驱动的。随着上游密度的变化，通过分离过程，通过全2D SOLPS建模，可以定量地再现各种离子源/汇的分流器剖面的分离以及功率损失的测量演变。

The process of divertor detachment, whereby heat and particle fluxes to divertor surfaces are strongly diminished, is required to reduce heat loading and erosion in a magnetic fusion reactor to acceptable levels. In this paper, the physics leading to the decrease of the total divertor ion current (It), or ‘roll-over’, is experimentally explored on the TCV tokamak through characterization of the location, magnitude and role of the various divertor ion sinks and sources including a complete analysis of particle and power balance. These first measurements of the profiles of divertor ionisation and hydrogenic radiation along the divertor leg are enabled through novel spectroscopic techniques. Over a range in TCV plasma conditions (plasma current and electron density, with/without impurity-seeding) the It roll-over is ascribed to a drop in the divertor ion source; recombination remains small or negligible farther into the detachment process. The ion source reduction is driven by both a reduction in the power available for ionization, Precl, and concurrent increase in the energy required per ionisation, Eion: this effect of power available on the ionization source is often described as ‘power starvation’ (or ‘power limitation’). The detachment threshold is found experimentally (in agreement with analytic model predictions) to be ~Precl/ItEion ~ 2, corresponding to a target electron temperature, Tt ~ Eion/γ where γ is the sheath transmission coefficient. The target pressure reduction, required to reduce the target ion current, is driven both by volumetric momentum loss as well as upstream pressure loss. The measured evolution through detachment of the divertor profile of various ion sources/sinks as well as power losses are quantitatively reproduced through full 2D SOLPS modelling through the detachment process as the upstream density is varied.

An improved understanding of the roles of atomic processes and power balance in divertor target ion current loss during detachment

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