Radiation effects in optical coatings for ITER diagnostics

Augusto Pereira, M. Medrano, E. Leon-Gutierrez, Carmen Pastor, Fernando Mota, Rafael Vila, Carmen Rodriguez, Ricardo Carrasco, Fernando Lapayese, Angel de la Peña, Alfonso Soleto, Esther Rincón, S. Cabrera, Vincente M. Queral, Alberto Fernández, Raquel López-Heredero, C. Torquemada, Tuesta Rodrigo, José Luis González Gómez, T. BelenguerLudo Vermeeren, Willem Leysen, Juan José Piqueras, Frédéric Le-Guern, Cristina Alén-Cordero

    Research outputpeer-review


    The aim is to provide an assessment of radiation damage in coated films on refractive substrates that could be used as relevant information to protect the field lenses in optical diagnostics for ITER. Radiation-resistant optical materials with transparent properties should transfer light from plasma to detectors through the interspace until the port cell area where they are located (more than 10 m from the vacuum window). These optical coatings and substrates should have resilience enough to withstand neutron and gamma irradiation without significant degradation of their transmittance. Coated sapphire (Al2O3 windows), YAG with Broad Band Anti-Reflective (BBAR) and substrates of BaF2/CaF2 protected with anti-humidity coating (Parylene-C) were extensively tested. After testing, transmission measurements and analysis of optical surfaces yield significant discoveries. All substrates showed good refractive performance under gamma radiation. On the contrary, Parylene-C did not resist temperatures above 100 degrees Celsius as expected, according to manufacturing specifications. In addition, it was observed that with an energy dose of 332 kGy of gamma rays and a significantly lower temperature of 50 degrees Celsius, the Parylene-C protection is also damaged. Coated sapphire had the best overall performance with respect to the neutron irradiation tests. Nevertheless, the decrease in transmission observed in the YAG and BaF2 coated samples is not significant for the expected cumulative neutron dose that these samples will receive at their location within the diagnostic. This information was considered for the selection of the best candidates as refractive lenses and optical coatings for the Preliminary Design Review (PDR) of ex-vessel components that will integrate the Wide-Angle Viewing System (WAVS) for ITER Equatorial Port 12. © 2023 Elsevier B.V.
    Original languageEnglish
    Article number113438
    Number of pages7
    Journalfusion engineering and design
    StatePublished - Mar 2023

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