Sinclair G, Tripathi J K, Diwakar P K, Hassanein A
Center for Materials Under Extreme Environment (CMUXE), School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907, USA.
Sci Rep. 2017 Sep 25;7(1):12273. doi: 10.1038/s41598-017-12418-z.
Transient events that occur during plasma instabilities in fusion reactors impart large heat fluxes onto the surrounding plasma-facing components (PFCs). Erosion and splashing of PFCs can contaminate the plasma and shorten material lifetime. Although tungsten is currently considered the most promising candidate material for future PFCs, concerns over the thermal shock performance during type-I ELMs (transient events expected in fusion devices) necessitate the study of other comparable materials. ELM-like heat loading was applied via a pulsed Nd:YAG millisecond laser on a pristine molybdenum (Mo) surface to measure surface melting and mass loss. One potential advantage of Mo is its higher specific heat of vaporization, which could lead to reduced particle emission. Imaging of the surface after loading revealed that complete surface melting began at 1.0 MJ m (heat load parameter of 31.62 MJ m s). Photon excitation also increased significantly above 1.0 MJ m, indicating possible phase change. At 1.4 MJ m (44.27 MJ m s), in situ mass loss measurements found an exponential increase in particle emission, indicating the presence of droplet formation and boiling. Direct comparisons of erosion during pulsed heat loading between PFC candidate materials will ensure that future fusion devices design components with optimal thermal strength.
聚变反应堆中等离子体不稳定性期间发生的瞬态事件会在周围面向等离子体的部件（PFC）上施加大量热通量。PFC的侵蚀和溅落会污染等离子体并缩短材料寿命。尽管钨目前被认为是未来PFC最有前景的候选材料，但对于I型边缘局域模（预计在聚变装置中出现的瞬态事件）期间的热冲击性能仍存在担忧，这就需要研究其他可比材料。通过脉冲钕钇铝石榴石毫秒激光对原始钼（Mo）表面施加类似边缘局域模的热负荷，以测量表面熔化和质量损失。钼的一个潜在优势是其较高的汽化比热，这可能会减少颗粒发射。加载后表面成像显示，在1.0兆焦/平方米（热负荷参数为31.62兆焦/平方米·秒）时开始完全表面熔化。在1.0兆焦/平方米以上，光子激发也显著增加，表明可能发生了相变。在1.4兆焦/平方米（44.27兆焦/平方米·秒）时，原位质量损失测量发现颗粒发射呈指数增加，表明存在液滴形成和沸腾现象。对PFC候选材料在脉冲热负荷期间的侵蚀进行直接比较，将确保未来聚变装置设计出具有最佳热强度的部件。
