Repetitive cleaning of a stainless steel first mirror using radio frequency plasma
Repetitive cleaning of a stainless steel first mirror using radio frequency plasma
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DOI：
10.1088/2058-6272/aa7629
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发表时间：
2017-05
影响因子：
1.7
通讯作者：
Jiao Peng;R. Yan;R. Ding;Junling Chen;Dahuan Zhu;Zengming Zhang
中科院分区：
文献类型：
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作者：
Jiao Peng;R. Yan;R. Ding;Junling Chen;Dahuan Zhu;Zengming Zhang
第一反射镜（FM）是当今托卡马克和未来聚变反应堆光学诊断系统的关键部件。由于它们接近燃烧的等离子体，它们的寿命应该是非常有限的，这极大地影响了相应诊断的安全操作。重复清洁有望为频繁更换受污染的FM提供解决方案，从而延长其使用寿命。采用射频等离子体对不锈钢FM样品进行了三次重复清洗循环，以评估每个循环过程中反射镜光学特性和形态的变化。在相同的条件下，在三个循环中，在镜面上沉积非晶碳膜。在三个周期相同的清洁参数，总反射率恢复高达95%。然而，随着连续的清洁循环，FM表面由于对晶界的破坏而逐渐变得粗糙。相应地，漫反射率在第二和第三循环后从百分之几增加到20%和27%。优化后的第二、三周期的清洗参数，表面粗糙度有了明显的降低，同时漫反射率的增加也有了明显的提高。
First mirrors (FMs) are crucial components of optical diagnostic systems in present-day tokamaks and future fusion reactors. Their lifetimes should be extremely limited due to their proximity to burning plasma, greatly influencing the safe operation of corresponding diagnostics. Repetitive cleaning is expected to provide a solution to the frequent replacement of contaminated FMs, thus prolonging their lifetimes. Three repetitive cleaning cycles using radio frequency plasma were applied to stainless steel (SS) FM samples, to evaluate the change of the mirrors' optical properties and morphology during each cycle. Amorphous carbon films were deposited on mirror surfaces under identical conditions in three cycles. In three cycles with identical cleaning parameters, the total reflectivity was restored at up to 95%. Nevertheless, with successive cleaning cycles, the FM surfaces gradually appeared to roughen due to damage to the grain boundaries. Correspondingly, the diffuse reflectivity increased from a few percent to 20% and 27% after the second and third cycles. After optimizing the cleaning parameters of the second and third cycles, the roughness showed a significant decrease, and simultaneously the increase of diffuse reflectivity was remarkably improved.