Radiation-hardening techniques of dedicated optical fibres used in plasma diagnostic systems in ITER

This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radiation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques.