Material selection and lifetime criteria for ESS target station

As the European Spallation Source (ESS) Target Station is nearing to its project completion, which is marked by “beam on target,” many target subsystems are passing the critical design reviews, which freeze the design and enable procurement and manufacturing. The selection of material for each target subsystem is important in delivering its designed functionality and reliability. The operational environment in the target station is quite demanding. The beam intercepting and beam stopping devices should manage the MW class proton beam with 4% duty factor, without failure. The subsystems which do not interact with the proton beam are exposed to a high level of neutron and gamma radiation fields. The high flux of radiation dose structurally and chemically degrades the material properties, which limits the lifetime of the affected systems. In this paper, we present the philosophy and current status of material selection and lifetime criteria for the ESS target station. Also, the visions for the materials research at ESS are presented.