Dynamics of the radiation-induced color centers in optical fibers for plasma diagnostics

In the past 2 years, we investigated up to 10 different types of silica optical fibers (optical fibers with an enhanced UV response, solarization resistant optical fibers, H2 loaded optical fibers), with a large core diameter (in this case 400 μm), and having various cladding materials. The research was carried out under gamma-ray, neutron and proton irradiation, both off-line and on-line. For the off-line measurements optical fibers were subjected to temperature stress between the irradiation steps (up to 250 °C, according to their cladding material). Depending on the optical fiber type, the manufacturing technology or the cladding material we noticed different aspects of the irradiation-induced optical attenuation, as different color centers are generated. Some of these color centers are partially reverted under high temperature exposure. For a better understanding of the irradiation-induced phenomena we decomposed the automatically acquired optical transmission spectra using a Gaussian deconvolution, for the color centers reported in the literature in the UV spectral range. The paper is a comparative study of these color centers dynamics in various optical fibers, for different irradiation conditions and, in same cases, under temperature stress.