Abstract

Contamination of ITER in-vessel components in accidents associated with the ingress of water from the cooling system into the vacuum vessel poses a threat to subsequent operation of the entire facility and individual diagnostic systems. In the present study, the process of degradation of the optical properties of single-crystal Mo mirrors, which are used in optical diagnostics, in their interaction with liquid water and water vapor is examined. The dynamics of variation of the specular reflection and diffuse scattering coefficients with exposure time and interaction mode is studied experimentally. It is demonstrated that the worst-case scenario (“steam event” in the ITER documentation) is modeled accurately by mirror exposure to distilled water at a temperature of ≈97°C. Samples of Mo mirrors with simulated contamination obtained in these experiments are used to test the operation of the plasma mirror cleaning system based on a direct- or pulsed-current abnormal glow discharge in a grid hollow cathode. It is demonstrated that the optical quality of Mo mirrors contaminated in simulated emergency events with water entering the vacuum vessel may be restored to near-baseline levels if Ar is used as the plasma-forming gas.

中文翻译：

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ITER水冷系统中模拟泄漏过程中钼镜降解的研究

摘要

与水从冷却系统进入真空容器相关的事故中，ITER船上组件的污染对整个设施和单个诊断系统的后续运行构成了威胁。在本研究中，研究了光学诊断中使用的单晶Mo镜与液态水和水蒸气相互作用时光学性能的下降过程。实验研究了镜面反射系数和漫散射系数随曝光时间和相互作用方式的变化。结果表明，最恶劣的情况（ITER文档中的“蒸汽事件”）是通过将镜子暴露于约97°C的蒸馏水中进行精确建模的。在这些实验中获得的具有模拟污染的Mo镜样品用于基于栅格空心阴极中的直流或脉冲电流异常辉光放电来测试等离子镜清洁系统的运行。结果表明，如果将Ar用作等离子体形成气体，则在模拟的紧急事件中被水进入真空容器污染的Mo镜的光学质量可以恢复到接近基线水平。