JET experience with the large scale cryogenic system

JET (Joint European Torus) is the world's largest running experimental device for the study of controlled nuclear fusion. A vital and integral part of JET is an extensive cryogenic system with six large scale cryopump systems which have to handle the process gas used during the fusion experiment. These cryopumps are supplied by two large He refrigerators and a liquid nitrogen storage and distribution plant. Operational experience with the JET cryosystem which has been one of the most reliable subsystems at JET since the beginning of the operation in 1983, will be discussed together with aspects of automatic operation and manpower and maintenance requirements. Stringent design and nuclear manufacturing standards enabled JET to obtain cryopump systems which are practically maintenance free and did not show any failure over 13 years of operation. (author)