Specific Features of Fiber Optics Application in ITER

Silica-based optical fibers have high transmission in the visible range and are widely used for transmitting light from plasma to detectors in modern fusion devices. Pure silica-core/F-doped silica-clad fibers are mainly applied for plasma diagnostics. The possible problems that can be encountered with fiber optics in ITER diagnostics are discussed. The neutron fluence to be accumulated in the bundles during the ITER lifetime is estimated. The results of the irradiation tests of the optical fibers at the fission reactor and the 14 MeV neutron generator are used for analysis of radiation resistance of the optical fibers. The results of radiation tests and neutron calculations prove the requirement to apply silica fibers with high radiation resistance in ITER. It is recommended to place the fiber bundles in the port cell behind the biological shielding, where the neutron flux from the plasma is attenuated to a value of ~10 7 n/(cm 2 s). The conclusion is made that it is possible to use the modern optical fibers in the plasma optical diagnostics (in a spectral range of 450–700 nm), the optical fibers being capable of surviving the radiation load during the whole ITER lifetime.