Vacuum pumping developments on the JET tokamak

Mechanical high vacuum pumping requirements at the JET facility, have historically been satisfied by modified commercially available 3500 l/s turbo-molecular pumps. These pumps have been used, over 17 years of experiments, but are now uneconomical to maintain due to obsolescence and tritium contamination. A novel adaptation of a new 2000 l/s turbo-drag pump has been developed to meet the present and future requirements. Two of these pumps have been installed and are used to pump the torus. These pumps offer a number of advantages, and systems on JET will continue to be upgraded to incorporate such pumps. These should be an effective solution for other large fusion experiments.