Investigation of boron distribution and material migration on the W7-X divertor by picosecond LIBS
Investigation of boron distribution and material migration on the W7-X divertor by picosecond LIBS
复制标题
利用皮秒 LIBS 研究 W7-X 偏滤器上的硼分布和材料迁移
DOI：
10.1088/1402-4896/ac4a93
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发表时间：
2022
期刊：
影响因子：
2.9
通讯作者：
D Naujoks
中科院分区：
文献类型：
--
作者：
D Zhao;S Brezinsek;R Yi;J Oelmann;L Cai;F Wu;G Sergienko;M Rasinski;M Mayer;C P Dhard;D Naujoks
抽象的。用皮秒激光诱导击穿光谱(PS-LIBS)研究了第二偏滤器工作阶段(OP1.2B)结束后从Wendelstein 7-X(W7-X)容器中回收的一组测试偏滤器单元(TDU)的水平靶元。用高深度分辨率分析了这些靶元上的B(B)分布、H图样和材料侵蚀/沉积图样，并在W7-X的极轴方向上进行了绘制。光谱分析表明，B、H、碳(C)和钼(Mo)等元素得到了明确的鉴定。通过三次渗硼过程中的B层沉积和W7-X等离子体操作以及B的多次侵蚀和沉积步骤，确定了偏滤器靶元上不均匀分布的B图案。与TDU一样，所分析的靶元是由细晶石墨制成的，但有两个标志层，这使得我们可以通过PS-Libs技术来确定材料的迁移。确定了两个净侵蚀带，其中一个主侵蚀带的峰值侵蚀深度为6.5μm，一个弱侵蚀带的峰值侵蚀深度为1.3μm。在两个净侵蚀带之间，利用PS-LIBS技术确定了一个宽度为135 mm、厚度可达3.5mLIBS的净沉积带。渗硼后各相中的B分布与W7-X标准磁组态的腐蚀/沉积模式和运行时间有关。这些靶元上含B层的厚度也与腐蚀/沉积深度有关，其中含B层的厚度在极向方向上的变化范围为0.1μm到6μm。
Abstract. One set of horizontal target elements of the Test Divertor Units (TDU), retrieved from the Wendelstein 7-X (W7-X) vessel after the end of second divertor Operation Phase (OP1.2B) in Hydrogen (H), were investigated by picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS). The Boron (B) distribution, H pattern and the material erosion/deposition pattern on these target elements were analyzed with high depth resolution and mapped in the poloidal direction of W7-X. From the spectroscopic analysis, B, H, Carbon (C) and Molybdenum (Mo) were clearly identified. A non-uniformly distributed B pattern on these divertor target elements was determined by the combination of B layer deposition during the three boronizations and W7-X plasma operation with multiple erosion and deposition steps of B. Like the TDU, the analyzed target elements are made of fine grain graphite, but have two marker layers which allow us to determine the material migration via the ps-LIBS technique. Two net erosion zones including one main erosion zone with a peak erosion depth of 6.5 μm and one weak erosion with a peak erosion of 1.3 μm were determined. Between two net erosion zones, a net deposition zone with width of 135 mm and a thickness up to 3.5 μm at the peak deposition location was determined by the ps-LIBS technique. The B distributions are correlated with the erosion/deposition pattern and the operational time in standard magnetic configuration of W7-X in the phases after the boronizations. The thickness of the containing B layer on these target elements also correlates with the erosion/deposition depth, in which the thickness of the containing B layer varies spatially in poloidal direction between 0.1 μm and 6 μm. Complementary, Focused Ion Beam combined with Scanning Electron Microscopy (FIB-SEM) was employed also to verify and investigate the deposition layer thicknesses at typical net erosion and net deposition zones as well as to identify the three boronizations in depth.