International audienceIn this review paper, we present radiation effects on silica-based optical fibers. We first describe the mechanisms inducing microscopic and macroscopic changes under irradiation: radiation-induced attenuation, radiation-induced emission and compaction. We then discuss the influence of various parameters related to the optical fiber, to the harsh environments and to the fiber-based applications on the amplitudes and kinetics of these changes. Then, we focus on advances obtained over the last years. We summarize the main results regarding the fiber vulnerability and hardening to radiative constraints associated with several facilities such as Megajoule class lasers, ITER, LHC, nuclear power plants or with space applications. Based on the experience gained during these projects, we suggest some of the challenges that will have to be overcome in the near future to allow a deeper integration of fibers and fiber-based sensors in radiative environments

We have determined the recoil range of spallation xenon produced by irradiation of Ba glass targets with approximatly 1190 and approximatly 268 MeV protons, using a catcher technique, where spallation products are measured in target and catcher foils. The inferred range for (sup 126)Xe produced in silicon carbide is approximatly 0.19 µm, which implies retention of approximatly 70% for (sup 126)Xe produced in "typical" presolar silicon carbide grains of 1 µm size. Recoil loss of spallation xenon poses a significantly smaller problem than loss of the spallation neon from SiC grains. Ranges differ for the various Xe isotopes and scale approximately linearly as function of the mass difference between the target element, Ba, and the product. As a consequence, SiC grains of various sizes will have differences in spallation Xe composition. In an additional experiment at approximatly 66 MeV, where the recoil ranges of (sup 22)Na and (sup 127)Xe produced on Ba glass were determined using gamma-spectrometry, we found no evidence for recoil ranges being systematically different at this lower energy. We have used the new data to put constraints on the possible presolar age of the SiC grains analyzed for Xe by Lewis et al. (1994). Uncertainties in the composition of the approximately normal Xe component in SiC (Xe-N) constitute the most serious problem in determining an age, surpassing remaining uncertainties in Xe retention and production rate. A possible interpretation is that spallation contributions are negligible and that trapped (sup 124)Xe/(sup 126)Xe is approximatly 5% lower in Xe-N than in Q-Xe. But also for other reasonable assumptions for the (sup 124)Xe/(sup 126)Xe ratio in Xe-N (e.g., as in Q-Xe), inferred exposure ages are considerably shorter than theoretically expected lifetimes for interstellar grains. A short presolar age is in line with observations by others (appearance, grain size distribution) that indicate little processing in the interstellar medium (ISM) of surviving (crystalline) SiC. This may be due to amorphization of SiC in the ISM on a much shorter time scale than destruction, with amorphous SiC not surviving processing in the early solar system. A large supply of relatively young grains may be connected to the proposed starburst origin (Clayton 2003) for the parent stars of the mainstream SiC grains

Extending our earlier work on cross sections for the production of residual nuclides by proton-induced reactions, the production of radionuclides from the target elements Ta, W, Pb, and Bi was investigated from thresholds up to 2.6 GeV using accelerators at LNS/Saclay, PSUVilligen, and TSUUppsala. Residual nuclides were measured by X-and i-spectrometry. We obtained more than 5000 new individual cross sections for 402 reactions. Together with the yet not published cross sections for the target elements Rb, Mo, Rh, Ag, In, Te and La and with published results of special investigations of cosmogenic nuclides, our entire consistent data base now covers the target elements C, N, 0, Mg, AI,

No abstract

The radiation sensitivity of chiral long period gratings was investigated for the first time. After a Co-60 gamma dose of 100 kGy they show radiation-induced changes of their transmission dip wavelength of up to 10 nm, which is 100 to 1000 times higher than the radiation-induced wavelength shift of different fiber Bragg grating types. They can therefore be used as radiation sensors down to doses of 10 Gy or even below, but not for accurate dose measurements since the size of the wavelength shift after a certain dose still depends on the radiation dose rate. Chiral gratings made of eight single mode fiber types with differences of their radiation-induced attenuation of several orders of magnitude were investigated in order to look for a correlation between dip wavelength shift and fiber attenuation. However, the dip wavelength curves do not show exactly the same order as the fiber attenuation curves. A theory that can exactly predict all properties of the chiral gratings might enable us to specify from our results an optimized fiber for the production of gratings that can also be used for radiation dosimetry.