Vacuum System  Illustration of the torus exhaust pumping system geometry, showing the four pumping ports with two cryopumps each. With a volume of 1,400 m³ and 8,500 m³ respectively, the ITER vacuum vessel and cryostat range amongst the largest vacuum systems ever built. Sophisticated techniques will be necessary for the monitoring and maintenance of these systems: once in operation, there will no longer be access to the machine.Vacuum pumping is required prior to starting the fusion reaction to eliminate all sources of organic molecules that would otherwise be broken up in the hot plasma. Vacuum pumping is also required to create low density—about one million times lower than the density of air. Mechanical pumps and powerful cryogenic pumps evacuate the air out of the vessel and the cryostat until the pressure inside has dropped to one millionth of normal atmospheric pressure. Considering the volume of ITER, this operation will take 24 to 48 hours.  The ITER model cryopump tested at the TIMO test facility in Karlsruhe, Germany. Photo: Forschungszentrum Karlsruhe (FZK). The main pumping systems are the eight torus exhaust pumps, the four cryopumps for the neutral beam injection systems used in plasma heating, and the two cryopumps for the ITER cryostat and the contained superconducting magnets. They will be cooled with supercritical helium.The complex pumps have been tailored for the very specific applications and requirements at ITER. |
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