Plasma response to lithium-coated plasma-facing components in the National Spherical Torus Experiment
Plasma response to lithium-coated plasma-facing components in the National Spherical Torus Experiment
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DOI：
10.1088/0741-3335/51/12/124054
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发表时间：
2009-11
影响因子：
2.2
通讯作者：
M. Bell;H. Kugel;R. Kaita;L. Zakharov;H. Schneider;B. LeBlanc;D. Mansfield;R. Bell;R. Maingi-R.-Ma
中科院分区：
文献类型：
--
作者：
M. Bell;H. Kugel;R. Kaita;L. Zakharov;H. Schneider;B. LeBlanc;D. Mansfield;R. Bell;R. Maingi-R.-Ma
国家球形环实验（NSTX）的实验表明，由于在石墨和碳纤维复合材料等离子体面对组件上涂覆锂涂层，对偏滤器等离子体的性能产生了有益的影响。这些涂层主要是通过安装在真空容器顶部的一对锂蒸发器施加的，该蒸发器将锂蒸气的准直流注入到下部偏滤器。在中性束注入（NBI）加热的氘H模式等离子体运行后立即应用锂，性能修改包括在等离子体密度的降低，特别是在边缘，和感应通量消耗，并增加电子和离子的温度和能量约束时间。减少边缘本地化模式（ELMs）的数量和幅度进行了观察，包括完整的ELM抑制的周期长达1.2秒，显然是由于改变边缘的稳定性。然而，在ELM被抑制的等离子体中，由于碳和中等Z金属杂质的增加，有效离子电荷Zeff和辐射功率有显著的长期增加，尽管不是锂本身，其在等离子体芯中保持在非常低的水平，<0.1%。杂质的积累可以通过重复触发ELMs与应用程序的n = 3的径向场扰动的短脉冲来抑制。锂在边缘密度上的降低也抑制了通过耦合到等离子体的ICRF功率的刮除层的寄生损耗，使波能够加热NBI产生的H模式等离子体核心中的电子。锂也已经通过将化学稳定的细锂粉末流直接注入到NBI加热的等离子体的刮除层中来引入。锂在SOL中被电离，并似乎沿着磁场流向偏滤器板。这种涂覆方法产生了与蒸发的锂类似的效果，但量较低。
Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on the performance of divertor plasmas as a result of applying lithium coatings on the graphite and carbon-fiber-composite plasma-facing components. These coatings have mostly been applied by a pair of lithium evaporators mounted at the top of the vacuum vessel which inject collimated streams of lithium vapor toward the lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode plasmas run immediately after the application of lithium, performance modifications included decreases in the plasma density, particularly in the edge, and inductive flux consumption, and increases in the electron and ion temperatures and the energy confinement time. Reductions in the number and amplitude of edge-localized modes (ELMs) were observed, including complete ELM suppression for periods of up to 1.2 s, apparently as a result of altering the stability of the edge. However, in the plasmas where ELMs were suppressed, there was a significant secular increase in the effective ion charge Zeff and the radiated power as a result of increases in the carbon and medium-Z metallic impurities, although not of lithium itself which remained at a very low level in the plasma core, <0.1%. The impurity buildup could be inhibited by repetitively triggering ELMs with the application of brief pulses of an n = 3 radial field perturbation. The reduction in the edge density by lithium also inhibited parasitic losses through the scrape-off-layer of ICRF power coupled to the plasma, enabling the waves to heat electrons in the core of H-mode plasmas produced by NBI. Lithium has also been introduced by injecting a stream of chemically stabilized, fine lithium powder directly into the scrape-off-layer of NBI-heated plasmas. The lithium was ionized in the SOL and appeared to flow along the magnetic field to the divertor plates. This method of coating produced similar effects to the evaporated lithium but at lower amounts.