Materials issues in high power accelerators

High power accelerators present a broad array of materials issues for scientists and design engineers. Some materials considerations are unique to accelerators per se, or to a particular accelerator. For example, high intensity stress waves and the resulting cavitation erosion in heavy liquid metal targets may occur where the sharpness of the beam pulse produces shock by thermal expansion. Other irradiation environment properties and materials response are similar to those for fission or fusion reactors. For example, the high displacement doses in the target structures of high power accelerators, produced by the impinging beam and the spallation neutrons, are of similar magnitude to those in high flux reactor cores and first walls of future fusion reactors. In addition to the central issue of radiation effects in metallic structural alloys, designers will be concerned with radiation effects in polymers and ceramics, which may be employed as seals, sensors, or insulators. Other applications place demands on materials that are not related to radiation but to other aspects of aggressive environments, such as compatibility of materials with special purpose fluids. Examples are discussed of problems, materials research and development solutions and recent experimental and calculational results.