Abstract This paper reports the gamma-ray irradiation effects on optical coatings and polarizers to be used in the ITER edge Thomson scattering system (ETS). Outside a diagnostic port-plug, in the Interspace, a total dose of the order of 1 MGy is expected through 20 years of ITER operation. In this study, gamma-ray irradiation experiments were performed up to 10 MGy. A high peak power laser beam, i.e. a pulse energy of 5 J and a pulse duration of ∼4 ns, is needed for a Thomson scattering measurement in ITER. Laser-induced damage threshold (LIDT) of anti-reflection (AR) and high-reflection (HR) coatings at the laser wavelengths after gamma-ray irradiation were investigated. LIDT of AR coating for 0° injections was more likely higher for the irradiated samples at a wavelength of 1064 nm. Regarding HR coatings, LIDT was not noticeably degraded by gamma-ray irradiation. Regarding polarizers, no degradation of transmission and extinction ratio was observed at visible and near infrared wavelength ranges when a wire-grid polarizer substrate is made of fused silica. Since a signal of ETS is almost linearly polarized, a wire-grid polarizer enables to improve signal to noise ratio of electron temperature and density measurements by Thomson scattering in ITER.

中文翻译：

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伽马射线对 ITER 边缘汤姆逊散射系统光学镀膜和偏振片的影响

摘要 本文报道了伽马射线辐照对 ITER 边缘汤姆逊散射系统 (ETS) 中使用的光学涂层和偏振器的影响。在诊断端口插头之外，在 Interspace 中，预计在 ITER 运行 20 年期间的总剂量约为 1 MGy。在这项研究中，进行了高达 10 MGy 的伽马射线辐照实验。ITER 中的汤姆逊散射测量需要高峰值功率激光束，即 5 J 的脉冲能量和~4 ns 的脉冲持续时间。研究了在伽马射线照射后激光波长下减反射 (AR) 和高反射 (HR) 涂层的激光诱导损伤阈值 (LIDT)。对于 1064 nm 波长的辐照样品，0° 注入的增透膜的 LIDT 更有可能更高。关于 HR 涂层，LIDT 不会因伽马射线辐射而显着降低。关于偏光片，当线栅偏光片基板由熔融石英制成时，在可见光和近红外波长范围内没有观察到透射率和消光比的降低。由于 ETS 的信号几乎是线性偏振的，线栅偏振器能够通过 ITER 中的汤姆逊散射提高电子温度和密度测量的信噪比。