Cryogenic Engineering Design of the ITER Superconducting Magnet Feeders

The ITER magnet system is to be operated at about 4.5 K. It has 31 feeders for high-current power supply, helium distribution and instrumentation cable routing. The feeders (except the smaller ones which are for instrumentation only) are 25 to 30 m long for about 40 tons. They have 3 main components: coil terminal box-cum-S-bend box (CTB-SBB), Cryostat feedthrough (CFT) and in-cryostat feeder (ICF). The CTB is the feeder component placed farthest from the coil (about 25 m away from the magnet center) and outside the bio-shield (the nuclear radiation restriction wall) so that it can be easily accessible in case the critical elements placed within it need maintenance: high-temperature superconducting current leads (HTSCL), large number of cryogenic control valves and pressure-release valves for quench protection. This paper explains the cryogenic design that considers these factors and main components.