High level gamma and neutron irradiation of silica optical fibers in CEA OSIRIS nuclear reactor

In the final objective of elaborating an optical sensor of dimensional change in a nuclear testing reactor, we present extreme high level irradiation tests, up to 1.3 10²⁰ n_fast/cm² and 16 GGy, conducted on high purity silica and hollow core photonic bandgap (PBG) fibers. These tests are performed in the OSIRIS reactor at CEA Saclay. We measure continuously Radiation Induced Absorption (RIA), at 3 optical wavelengths: 980 nm, 1064 nm and 1310 nm. The evolution with the time of the spectral dependency over larger wavelength range is also reported. As well as reporting RIA up to higher dose than presented before, we demonstrate here the excellent superiority of hollow core PBG fibers over their conventional counterparts in term of radiation resistance up to over 10²⁰ n_fast/cm² and 10 GGy. We also report some Optical Time Domain Reflectometry (OTDR) measurements that probe the irradiated parts of the fibers and show how optical scattering first increases then finally decreases when the silica goes from un-irradiated silica to the metamict state.