For transmissive optics, radiation-induced darkening is a particularly serious concern. Highly pure SiO2 and CaF2 have been irradiated and the increased absorption coefficients compared with known color centers. The possibility of reducing the damage through annealing at elevated temperature has been evaluated. In addition, molecular dynamics calculations of 14 MeV neutron collisional cascades and their resulting defects will be discussed and the results compared with experiments.
For reflective optics, the primary design option considered is grazing-incidence metal mirrors. For these, the most serious concern is reduction in laser damage threshold due to long-term exposure and contamination. Unstable surface deformations due to operation at grazing incidence angles are possible and will be evaluated. Both experiments on LIDT and modeling of defects will be presented.
Future R&D needs and prospects for extrapolation to IFE power plants will be discussed.