Report on TESCA irradiation of optical sensors and tests of glasses

The TESCA irradiation campaign, conducted from November 16 to December 17, 2023 (one reactor operating cycle) in the SCK•CEN BR2 research reactor, enabled testing of optical sensors at different development stages, under intense radiation: fast neutron fluence (E > 1 MeV) of 1 to 2 x 10 19 neutrons/cm 2 and gamma dose of about 5 GGy. The temperature ranged between 100°C and 500°C. TESCA irradiation enabled on-line testing of Fabry-Perot extensometers, and miniature, non-contact, high-temperature optical pyrometry sensors. We also report an online measurement of radiation-induced attenuation on a sapphire sample. Because all sensors and measurements are temperature-sensitive, it was crucial to either maintain stable temperatures or accurately monitor them to assess the impact of radiation on sensor response stability at constant load or on glass parameters. Brief temperature jumps were also applied to test sensors accuracy. An overview of results from monitoring the various sensors and experiments throughout the irradiation cycle are provided. A well thermally stabilized Fabry–Perot extensometer maintained high stability, with a drift below 1 µm under constant load. It also ensured accurate thermal expansion measurements during temperature jumps. The pyrometric sensors operated effectively under intense irradiation at steady temperature: the collected blackbody emission spectrum was preserved, as expected with constant temperature. The unusable spectral range around the OH peak will be extended to [1250–1430 nm]. In contrast, the RIA setup showed susceptibility to temperature variations and mechanical vibrations, indicating the need for improved mechanical robustness.