Fiber optics for plasma diagnostics in ITER

The work is related to literature survey and study to find out the proper fiber optics for visible plasma diagnostics in ITER. The silica-based optical fibers have high transmission in the visible range and they are widely used for transmitting light from plasma to detectors in the modern thermonuclear facilities. The fiber bundle consists as a rule of several tens or hundreds optical fibers of the 100-600 mu m diameter. In ITER the fiber bundles extend from radiation field area of the region near the plasma up to the diagnostic room at the distance about 100 m. The lifetime of the optical fiber in ITER should be more than 15 years and the radiation hardness is a major problem for the fiber optics. The estimations of the neutron fluxes at the expected places of the fiber bundle location are given. A brief review is presented for the irradiation tests of the optical fibers. The fiber optics will suffer from radiation-induced optical absorption and radioluminescence. It is shown that the pure silica-core/F-doped silica-clad fibers and H-2 doped silica core fibers are the best for ITER application. The analysis of the irradiation tests and the neutron calculations shows that radiation resistance of the modern optical fibers provides the opportunity for its application in ITER in the spectral range 450-1300 nm. (C) 2017 Elsevier B.V. All rights reserved.