Low activation materials applicable to the IFMIF accelerator

The International Fusion Materials Irradiation Facility (IFMIF) is an intense neutron source for developing fusion materials. Stable and continuous operation is of primary importance. The radioactivity produced in the accelerator components due to the deuteron beam loss prolongs the cooling time and may pose a potential limit to the proposed availability of 70%. As such radioactivity is produced by deuteron beam loss and secondary neutrons with energy up to 50 MeV, the materials selection is important for minimizing the radioactivity after about one day cooling time. The major components of accelerator are selected by multiple engineering reasons, so the beam loss should be controlled to restricted areas and proper materials applied there. From an analysis of induced radioactivities in candidate materials, the beam loss along the linac needs to be reduced below ∼5 nA/m. The arrangements and suitable materials for a scraper to realize the required beam loss limit are presented.