Physics conclusions in support of ITER W divertor monoblock shaping
Physics conclusions in support of ITER W divertor monoblock shaping
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DOI：
10.1016/j.nme.2017.03.005
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发表时间：
2017-08-01
影响因子：
2.6
通讯作者：
Watkins, J. G.
中科院分区：
文献类型：
--
作者：
Pitts, R. A.;Bardin, S.;Watkins, J. G.
ITER钨(W)偏滤器剩余的关键物理设计问题是在主动冷却靶区的高热流密度靶区的单块(MB)前表面成形问题。工程公差规范规定环向相邻主梁之间的最大径向步长为0.3 mm，具有挑战性。假定平行热载荷的光学投影，在燃烧等离子体运行期间和边缘局域模式(ELM)或中断诱导功率加载期间的瞬时条件下，如果要避免准稳态熔化，则需要对这些边缘进行磁阴影。2013年，一项旨在调查ITER瞬时W边缘融化后果的JET实验发现，基于简单的几何论证，预期边缘功率负载存在显著缺陷，这让人们对粗略观察场线角度的边缘负载的理解产生了怀疑。因此，通过国际托卡马克物理活动(托卡马克物理活动)和热核实验堆合同，启动了一项协调的多实验和模拟工作，目的是从边缘功率负载和熔体动力学的角度改善支持甲基溴成形决定的物理基础。本文报告了这一活动的结果，首先得出结论：径向失调极向前沿功率负载的几何近似确实是有效的。在此基础上，比较了定形和非定形块体表面在有熔化和无熔化的静态和瞬变载荷作用下的行为，以考察熔化或功率过载的后果，以及成形是否有益。本文认为，在ITER偏滤器靶的高热流区，建议采用MB顶面整形来遮挡极向间隙边缘。(C)2017由爱思唯尔有限公司出版。这是一篇CC BY-NC-ND许可证下的开放获取文章。
The key remaining physics design issue for the ITER tungsten (W) divertor is the question of monoblock (MB) front surface shaping in the high heat flux target areas of the actively cooled targets. Engineering tolerance specifications impose a challenging maximum radial step between toroidally adjacent MBs of 0.3 mm. Assuming optical projection of the parallel heat loads, magnetic shadowing of these edges is required if quasi-steady state melting is to be avoided under certain conditions during burning plasma operation and transiently during edge localized mode (ELM) or disruption induced power loading. An experiment on JET in 2013 designed to investigate the consequences of transient W edge melting on ITER, found significant deficits in the edge power loads expected on the basis of simple geometric arguments, throwing doubt on the understanding of edge loading at glancing field line angles. As a result, a coordinated multi-experiment and simulation effort was initiated via the International Tokamak Physics Activity (ITPA) and through ITER contracts, aimed at improving the physics basis supporting a MB shaping decision from the point of view both of edge power loading and melt dynamics. This paper reports on the outcome of this activity, concluding first that the geometrical approximation for leading edge power loading on radially misaligned poloidal leading edges is indeed valid. On this basis, the behaviour of shaped and unshaped monoblock surfaces under stationary and transient loads, with and without melting, is compared in order to examine the consequences of melting, or power overload in context of the benefit, or not, of shaping. The paper concludes that MB top surface shaping is recommended to shadow poloidal gap edges in the high heat flux areas of the ITER divertor targets. (C) 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.