Studies on proton irradiation-induced modifications of KU1 quartz glass ultraviolet transmission properties

The optical transmission components of the future thermonuclear reactor will be expected to maintain their transmission properties under high levels of ionizing radiation for hundreds of hours. The degradation of the optical transmission properties of the candidate materials has to be studied to assess the lifetimes of such systems. KU1 quartz glass, known to be a radiation-resistant insulator material, is a potential candidate for manufacturing diagnostics windows and optical fibers for the ITER project. Some KU1 samples were irradiated with 12.6 MeV protons in the Bucharest Tandem accelerator to study their ultraviolet (UV) transmission properties modification. In the absorption spectra, the presence of a 215 nm peak and a big reduction of the 260 nm peak were observed. The effects of the 12.6 MeV proton irradiation on KU1 quartz glass optical properties were compared with the effects on similar KU1 samples irradiated with gammas and high-energy electrons at CIEMAT, Madrid. The comparison led to the conclusion that the saturation effect in absorption for proton is obtained at a 10 MGy irradiation dose, while the same effect is obtained at 4–5 MGy for gamma rays and 11–12 MGy for electrons, suggesting that the ionization process is essential for the formation of defect absorption centers.