R&D progress for the ITER vacuum pumping system

Within the frame of the European Fusion Programme Forschungszentrum Karlsruhe is charged to develop the vacuum systems for ITER. These activities comprise the high vacuum systems for the torus exhaust gas, the neutral beam injectors and the cryostat, as well as the mechanical forepump trains for all of these systems. This paper describes the several systems and gives an overview about the underlying R&D work performed to provide a design basis for large vacuum pump systems. Most of the presented cryosorption results have been measured in the TIMO test bed, which houses an approximately 1:2 scale model of the torus cryosorption pump. In TIMO, almost all ITER relevant conditions can be replicated (like operational times, coolant flows, gas flows, temperatures, pressure), except of the pumping of tritium. The latter issue will be dealt with in a dedicated experiment during the 2003 trace tritium campaign in JET. It is shown that cryosorption vacuum pumping is an efficient and robust technique to be employed for ITER. Concepts for an appropriate forepump train for the high vacuum pumps are also discussed.