The vacuum systems of ITER

ITER is a large vacuum facility which comprises many service, diagnostic and monitoring vacuum sub-systems as well as three large cryogenic pumping systems for evacuation and maintenance of the requested pressure levels. The presence of hydrogen (including the radioactive isotope tritium) and exclusion of other gases defines the parameters of fusion vacuum systems. This paper will focus on the areas of the ITER vacuum systems which require customized developments and cannot rely on commercial solutions. The complex pumps have been tailored for the very specific applications and requirements at ITER, characterized by high magnetic and radiation fields, excellent availability and maintainability and, especially, the need to be tritium-compatible. An outline of the development path which was needed to come up with a sound design for the ITER cryopumps is given and the status of the programme in view of the imminent manufacturing phase is described in this paper.