High-density experiments with hydrogen ice pellet injection and analysis of pellet penetration depth in Heliotron J
High-density experiments with hydrogen ice pellet injection and analysis of pellet penetration depth in Heliotron J
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DOI：
10.1088/1361-6587/ab1d40
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发表时间：
2019-07-01
影响因子：
2.2
通讯作者：
Watanabe, K. Y.
中科院分区：
文献类型：
--
作者：
Motojima, G.;Okada, H.;Watanabe, K. Y.
研制了一种低温氢气球团注入系统，并将其应用于高密度实验。在Heliotron J中，采用锥形结构的低速小颗粒喷射筒进行颗粒喷射加注。将速度为260 +/- 30 m s（-1）、典型尺寸为1.1-1.2 mm的单个颗粒注入NBI + ECH等离子体和仅NBI等离子体中。在这两种情况下，在颗粒注射后观察到电子密度显著增加。在两种情况下，由于颗粒注入导致的线平均电子密度增加为4.0 +/- 0.7 x 10(19) m（-3）。颗粒加注导致高电子密度状态下的高存储能量。注入微球后，在纯nbi等离子体中获得了高核密度的峰值电子密度分布图，而边缘密度保持在较低的水平。创新的h - α阵列测量结果表明，在NBI + ECH等离子体中，颗粒已经穿透到磁轴，而在仅NBI等离子体中，颗粒的穿透深度超出了磁轴，比NBI + ECH等离子体的深度更深。烧蚀程序的模拟结果不能解释穿透深度的差异，其中没有考虑快速电子/离子对球团烧蚀的影响。这些结果表明，为了解释目前的实验结果，在烧蚀代码中应该考虑快电子/离子的影响。
A hydrogen cryogenic pellet injection system was fabricated and applied to high-density experiments in a Heliotron J device. The fueling through pellet injection was conducted in Heliotron J by using an injection barrel with a tapered structure for a small pellet with low speed. A single pellet with a speed of 260 +/- 30 m s(-1) and a typical size of 1.1-1.2 mm was injected into NBI + ECH plasmas and NBI-only plasmas. In both cases, a significant increase in electron density was observed upon pellet injection. The increase in line-averaged electron density due to pellet injection was 4.0 +/- 0.7 x 10(19) m(-3) in both cases. Pellet fueling leads to high stored energy in the high-electron-density regime. A peaked electron density profile with high core density is obtained in NBI-only plasmas after pellet injection, while the edge density is kept at a lower level. An innovative H-alpha array measurement shows that the pellet has penetrated into the magnetic axis in NBI + ECH plasmas, while the penetration depth in NBI-only plasmas is beyond the magnetic axis, which is deeper than that in NBI + ECH plasmas. The difference in penetration depth cannot be explained by the simulation results of the ablation code, in which the effect of fast electrons/ions on pellet ablation is not considered. These results suggest that the effect of fast electrons/ions should be taken into account in the ablation code in order to explain the present experimental results.