Abstract For the fusion reactor ITER, a mandatory monitor of the fusion device and plasma will be performed with optical diagnostic systems. For the metallic first mirrors, the recovery of the reflectivity losses due to dust deposition is proposed to be carried out for 14 different optical diagnostic systems by the plasma cleaning technique. In this work, we studied the influence of the electrode area on the electrode potential as a function of the applied power with a 60 MHz radio very high frequency source. Unshielded copper disks with different diameters were constructed to study the impact of the electrode area in the range of 90 cm2 to 1200 cm2, which corresponds to an Edge Thomson Scattering area ratio of 0.15 to 2. It was observed that the absolute value of the resulting bias decreased from 280 V to 15 V with the increase of the area for a given RF power. Moreover, the power consumption was reduced by 43 % using a pre-matching element close to the vacuum feedthrough. The cleaning homogeneity on a curved and a large size mirror was studied, and the difference between the center and edge maximum/minimum was around 20 % and 40 % for the curved and large size mirror, respectively. For ITER, it is required to have an End-of-Cleaning Indicator (ECI), which shows when the cleaning process would be stopped. In this work, we studied the feasibility of Optical Emission Spectroscopy (OES) as a real-time control tool for the RF cleaning process. With 13.56 or 60 MHz, it was possible to use OES as ECI by following the molybdenum (Mo), rhodium (Rh), and aluminum (Al) emission lines. The decrease of Al I line and increase of the Mo I and Rh I line were recorded as a function of the cleaning time.

中文翻译：

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使用 60 MHz 甚高频进行 ITER 光学诊断的射频放电镜清洁

摘要 对于聚变反应堆 ITER，将通过光学诊断系统对聚变装置和等离子体进行强制监测。对于金属第一反射镜，建议通过等离子体清洁技术对 14 种不同的光学诊断系统进行因灰尘沉积造成的反射率损失的恢复。在这项工作中，我们研究了电极面积对电极电位的影响，作为使用 60 MHz 无线电甚高频源施加的功率的函数。构建了不同直径的非屏蔽铜盘来研究电极面积在 90 cm2 到 1200 cm2 范围内的影响，这对应于 0.15 到 2 的边缘汤姆森散射面积比。据观察，对于给定的 RF 功率，随着面积的增加，所得偏置的绝对值从 280 V 下降到 15 V。此外，使用靠近真空馈通的预匹配元件，功耗降低了 43%。研究了曲面镜和大尺寸镜子的清洁均匀性，曲面镜和大尺寸镜子的中心和边缘最大值/最小值之间的差异分别约为 20% 和 40%。对于 ITER，需要有一个清洁结束指示器 (ECI)，显示清洁过程何时停止。在这项工作中，我们研究了发射光谱 (OES) 作为射频清洁过程实时控制工具的可行性。在 13.56 或 60 MHz 频率下，可以按照钼 (Mo)、铑 (Rh)、和铝 (Al) 发射线。Al I 线的减少和 Mo I 和 Rh I 线的增加被记录为清洗时间的函数。