Island divertor experiments on the W7-AS stellarator-猫眼课题宝

DOI：

10.1088/0741-3335/43/12a/313

发表时间：

2001-11

期刊：

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其他

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作者：

F. Gadelmeier;P. Grigull;K. Mccormick;R. Brakel;R. Burhenn;H. Ehmler;Y. Feng;L. Giannone;D. Hartmann;D. Hildebrandt;R. Jaenicke;J. Kisslinger;T. Klinger;J. Knauer;R. König;D. Naujoks;E. Pasch;F. Sardei;F. Wagner;U. Wenzel;A. Werner;W. Team

1. 过去，在限制条件下，在W7-AS中不可能产生高功率、高密度、准平稳中性束注入（NBI）放电。这样的放电倾向于表明杂质积累，缺乏密度控制和随后的辐射坍塌（正常约束）。目前，W7-AS采用模块化、开放式岛式分流器，与W7-X类似。导流器可以进入新的NBI加热、高密度（最高可达4.10 - 20 m -3）工作状态（高密度h模式）。它存在于阈值密度以上，具有平坦的密度分布、高能量、低杂质约束时间和边缘局域辐射的特点。hdh模式与之前在W7-AS中观察到的无elm的h模式非常相似，但与之相反的是，这些模式避免了杂质的积累。这些新特性可以实现全密度控制和准稳态运行（目前仅受NBI可用性的技术限制），也可以在部分脱离转向器目标的条件下进行。在hdh模式下，即使在附加排放中，分流器的目标载荷也大大降低。这主要是由于有利的上游条件（较高的nes）、边缘局部辐射和功率沉积宽度的增加。hdh模式的好处不仅限于氢等离子体。它们也发生在氘等离子体中——尽管是以一种改良的方式。毫无疑问，氢和氘的放电之间存在明显的同位素效应。在W7-AS中获得的结果为W7-X提供了良好的前景，并支持岛屿导流器概念作为边缘磁岛器件的重要候选。2. 图1总结了能量约束时间E =W/Pabs、归一化辐射功率Prad/Pabs以及准平稳放电（Pabs=1.4 MW）获得的分离矩阵密度nes随线平均密度ne的变化规律。在NC模式下，E值为0.26·a 0.4·Bt 0.83·a 2.21·R 0.65·ne 0.51·Pabs -0.59,[2]，而在hdh模式下，E值为E ~ 2·E ISS95。P rad /P abs随ne平稳增长，直到部分等离子体脱离，此时发生归一化辐射功率的跳跃。分离矩阵密度在NC - hdh模式过渡点急剧增加，然后随着ne继续攀升并达到饱和

1. Abstract In the past, under limiter conditions, it has been impossible to produce high-power, highdensity, quasi-stationary neutral beam injection (NBI) discharges in W7-AS. Such discharges tended to evince impurity accumulation, lack of density control and subsequent radiation collapse (Normal Confinement). Presently, W7-AS is operating with a modular, open island divertor similar to that foreseen for W7-X. The divertor enables access to a new NBI heated, high density (ne up to 4·10 20 m -3 ) operating regime (High Density H-mode). It is extant above a threshold density, and is characterized by flat density profiles, high energyand low impurity confinement times and edge-localized radiation. The HDH-mode shows strong similarity to ELM-free H-mode scenarios previously observed in W7-AS, but in contrast to these avoids impurity accumulation. These new features enable full density control and quasi steady-state operation over many confinement times (at present only technically limited by the availability of NBI) also under conditions of partial detachment from the divertor targets. In HDH-mode, even in attached discharges, the divertor target load is considerable reduced. This is mainly due to favourable upstream conditions (higher nes), edge localized radiation and increased power deposition width. The benefits of the HDH-mode do not restrict only to hydrogen plasmas. They also occur ‐ albeit in a modified manner ‐ in deuterium plasmas. Undoubtedly, there are clear isotope effects between hydrogen and deuterium discharges. The results obtained in W7-AS render good prospects for W7-X and support the island divertor concept as a serious candidate for devices with magnetic islands at the edge. 2. Results Fig. 1 summarizes the behaviour of the energy confinement time E =W/Pabs, the normalized radiated power Prad/Pabs, and separatrix density nes obtained from quasi-stationary discharges with Pabs=1.4 MW as a function of the line-averaged density ne. E-values in NC follow the scaling E ISS95 =0.26· a 0.4 ·Bt 0.83 ·a 2.21 ·R 0.65 ·ne 0.51 ·Pabs -0.59 , [2], whereas for the HDH-mode one finds E ~ 2· E ISS95 . P rad /P abs grows smoothly with ne until partial plasma detachment, where a jump in the normalized radiated power occurs. The separatrix density n es increases sharply at the NC HDH-mode transition point, then continues to climb with ne and saturates

Island divertor experiments on the W7-AS stellarator

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