Plasma wall interaction and its implication in an all tungsten divertor tokamak
Plasma wall interaction and its implication in an all tungsten divertor tokamak
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DOI：
10.1088/0741-3335/49/12b/s04
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发表时间：
2007-12
影响因子：
2.2
通讯作者：
R. Neu;M. Balden;V. Bobkov;R. Dux;O. Gruber;A. Herrmann;A. Kallenbach;M. Kaufmann;C. Maggi
中科院分区：
文献类型：
--
作者：
R. Neu;M. Balden;V. Bobkov;R. Dux;O. Gruber;A. Herrmann;A. Kallenbach;M. Kaufmann;C. Maggi
ASDEX升级最近完成了向全W偏滤器托卡马克的过渡，将最后剩下的石墨瓦换成了涂W的石墨瓦。在未预先硼化的情况下进行等离子体启动。有人发现，在等离子体中的大的He含量，从直流辉光放电调节，导致约束减少。在改变为D辉光进行激发间调节后，He含量迅速下降，并且同时实现了H因子接近1的通常H模式限制。在初始调节阶段之后，可以实现与之前的硼化活动类似的氧浓度。尽管去除了所有的宏观碳源，但到目前为止，没有观察到C流入和C含量的强烈变化。的W浓度是类似的，以前在旧的硼化放电和只有部分覆盖的表面与W测量。同时发现，虽然在偏滤器中的W侵蚀通量在大多数情况下大于主室中的W源，但它对主等离子体中的W含量仅起次要作用。对于大的天线距离和强的气体抽吸，ICRH功率耦合可以被优化以减少W流入。这允许存储能量的类似增加，如用可比较的束功率产生的。然而，一个强大的辐射功率的增加和H模式的损失被观察到的高温边缘等离子体接近天线的条件。ECRH的使用允许保持W浓度的中心峰值较低，并且已经实现了改进的H模式的甚至阶段。
ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.