Subscribe options

Select your newsletters:

Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Cryolines | Another day, another spool

    Having wedged his body and equipment into the cramped space between the ceiling and the massive pipe, a worker is busy welding two cryolines spools. A few metre [...]

    Read more

  • Image of the week | Bearings unveiled

    The construction teams are in the last stages of preparing the Tokamak pit for the first major operation of ITER machine assembly: the lowering of the cryostat [...]

    Read more

  • Technology | Perfecting tritium breeding for DEMO and beyond

    While ITER will never breed tritium for its own consumption, it will test breeding blanket concepts—the tools and techniques that designers of future DEMO react [...]

    Read more

  • Fusion world | Japan and Europe complete the assembly of JT-60SA

    The JT-60SA fusion experiment in Naka, Japan, is designed to explore advanced plasma physics in support of the operation of ITER and next-phase devices. After s [...]

    Read more

  • Manufacturing | Thermal shield milestone in Korea

    Six years after the start of fabrication, Korean contractor SFA has completed the last 40° sector of vacuum vessel thermal shield. The stainless steel panels, c [...]

    Read more

Of Interest

See archived entries

Cryopumps: fewer, cheaper and no less efficient

Robert Arnoux

 (Click to view larger version...)
In the pre-2001 design, when ITER was to be nearly the size of Saint-Peter's Basilica in Rome, 16 cryopumps were to be accommodated at the divertor level of the vacuum vessel.

Cryopumps have the essential function of removing impurities and helium ash from the plasma, enabling the plasma to continue to burn and produce fusion power.

The requirements for vacuum pumping are linked to the plasma fuelling rates—even in the "smaller" ITER these had to be maintained. Design developments in cryo-pumping allowed the machine to be optimized with ten cryopumps in 2001 and eight in 2003.

Eight cryopumps has been the Baseline design figure until recently, when the ITER Director-General proposed to simplify the divertor ports of the machine and remove all "T-shaped" branch ducts. This left only five or six positions where cryopumps could be placed.

This bold proposal was quite a challenge for the ITER vacuum team. "Let's say our creativity was strongly stimulated..." recounts ITER Vacuum Section Head, Robert Pearce. "A five-pump solution was proposed, but this was considered rather risky for the goal of achieving ITER's fusion power mission."

Following discussions at the Science and Technology Advisory Committee (STAC) in November 2011 and at the Ninth ITER Council later that month, a much improved solution was found: there would be six divertor cryopumps in ITER doing the job that was originally assigned to sixteen.

"Basically, improvements in the cryopumping system design over many years have allowed the cryopumps to sit in bigger housings, enabling them to pump longer and store more gas and impurities," says Robert. The new housings are "simpler" and have a volume of greater than 14 m³, as compared to 8 m³ in 2003. As the pumping configuration at the bottom of the machine (divertor level) was changed, it became possible to make improvements that resulted in the easier integration of other systems.

"We think that the overall six-pump solution is better in the end: we now have six identical systems. Operations are made simpler and the performance of the system is not affected," conclude Robert and his vacuum team.

Considering that each branch duct and cryopump is a multimillion-euro component, the savings for the ITER Project are considerable.


return to the latest published articles