The next generation thermonuclear fusion machine ITER comprises three large cryogenic pumping systems. These are the torus exhaust pumping system of eight identical cryopumps (each having a molecular flow pumping speed of about 50 m3/s) located in four pumping ports, the cryopumps for the neutral beam injection systems for plasma heating (with a pumping speed of about 4000 m3/s per injector), and two cryopumps for the ITER cryostat (similar to the torus cryopumps). All customized cryopumps are force-cooled with supercritical helium and share a similar modular design of charcoal-coated cryosorption pumping panels.
The complex pumps have been tailored for the very specific applications and requirements at ITER. A pre-requisite for a successful design is a reliable and parametric data-base. This was generated over several operational years with the ITER model cryopump (half scale in many aspects, with 4 m2 pumping surface), installed in the TIMO test bed at Forschungszentrum Karlsruhe. The experiments have been finalized in 2006 and the results were used to develop the detailed design of the ITER prototype torus cryopump which is currently under manufacturing in European industry.
The paper presents an overview of the investigated test categories and highlights some of the most essential results. The model pump was comprehensively characterised in vacuum performance aspects (pumping speed, flow rates, pressures, regeneration requirements), cryogenic aspects (heat loads under normal pumping and regeneration) and safety aspects (hydrogen accumulation, loss of vacuum accident, sorbent poisoning), all relevant for ITER operation
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