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Helium flux effects on bubble growth and surface morphology in plasma-facing tungsten from large-scale molecular dynamics simulations

机译：大规模分子动力学模拟中的氦通量对面向等离子体的钨中气泡生长和表面形态的影响

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摘要

We investigate helium flux effects on helium transport and surface evolution in plasma-facing tungsten using molecular dynamics. The simulations span two orders of magnitude, from ITER-relevant levels to those more typical of simulations published to date. Simulation times of up to 2.5 mu s (corresponding to actual fluences of 1.4 x 10(21) m(-2)) are achieved, revealing concerted bubble-bursting events that are responsible for significant and very sudden changes in surface morphology. The depth distribution of helium depends very strongly on helium flux: helium self-trapping becomes more probable near the surface at high flux, and a layer of near-surface bubbles forms. Helium retention prior to the onset of bubble bursting is also substantially lower at low flux than it is at high flux. Surface features at low fluence arc correlated with the positions of bubbles, but at high fluence, bubbles tend to coalesce, venting to the surface at one or more locations and leaving large interconnected cavities below the surface. Ruptured bubbles may serve as pathways deeper into the material, allowing helium to bypass the layer of near-surface bubbles and fill deeper, potentially much larger, bubbles that can produce more substantial surface features. Deeper bubbles also emit prismatic dislocation loops that can fill in cavities closer to the surface. Our results suggest that nearly all molecular dynamics simulations published to date are hampered by finite-size effects, and that helium flux is a very important parameter in determining the behavior of helium in plasma-facing components.
机译：我们使用分子动力学研究了面向等离子体的钨中氦通量对氦运输和表面演化的影响。这些模拟跨越两个数量级，从与ITER相关的水平到迄今为止更为典型的模拟。实现了高达2.5μs的模拟时间（对应于1.4 x 10（21）m（-2）的实际通量），揭示了协调一致的气泡破裂事件，这些事件导致表面形态发生了重大且非常突然的变化。氦的深度分布在很大程度上取决于氦通量：在高通量下，氦自陷在表面附近的可能性更大，并且会形成一层近表面的气泡。气泡破裂前的氦气滞留量在低通量下也比在高通量下要低得多。低通量的表面特征与气泡的位置相关，但是在高通量下，气泡趋于聚结，在一个或多个位置处排放到表面，并在表面下方留下较大的互连腔。破裂的气泡可以充当更深层进入材料的通道，从而使氦气绕过近表面气泡层，并填充更深的，可能更大的气泡，从而产生更实质的表面特征。更深的气泡还会发出棱柱形的位错环，这些位错环可以填充更靠近表面的空腔。我们的结果表明，迄今为止，几乎所有已发布的分子动力学模拟都受到有限尺寸效应的阻碍，并且氦通量是确定面向等离子体的部件中氦的行为时非常重要的参数。

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  • 来源
    《Nuclear fusion》 |2019年第6期|066035.1-066035.21|共21页
  • 作者

    Hammond Karl A.; Naeger Ian V; Widanagamaachchi Wathsala; Lo Li-Ta; Maroudas Dimitrios; Wirth Brian D.;

  • 作者单位

    Univ Missouri, Dept Chem Engn, Columbia, MO 65211 USA|Univ Missouri, Nucl Engn Program, Columbia, MO 65211 USA;

    Univ Missouri, Dept Chem Engn, Columbia, MO 65211 USA;

    Univ Utah, Sci Comp & Imaging Inst, Salt Lake City, UT 84122 USA|Univ Utah, Internal Med, Salt Lake City, UT 84122 USA;

    Los Alamos Natl Lab, Data Sci Scale Team, Los Alamos, NM 87545 USA;

    Univ Massachusetts, Dept Chem Engn, Amherst, MA 01003 USA;

    Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA|Oak Ridge Natl Lab, Fus & Mat Nucl Syst Div, POB 2009, Oak Ridge, TN 37831 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    tungsten; helium; molecular dynamics; fuzz; bubble;

    机译：钨;氦;分子动力学;绒毛;气泡;

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