Subscribe options

Select your newsletters:

Please enter your email address:

@

Your email address will only be used for the purpose of sending you the ITER Organization publication(s) that you have requested. ITER Organization will not transfer your email address or other personal data to any other party or use it for commercial purposes.

If you change your mind, you can easily unsubscribe by clicking the unsubscribe option at the bottom of an email you've received from ITER Organization.

For more information, see our Privacy policy.

News & Media

Latest ITER Newsline

  • Vacuum components | Shake, rattle, and... qualify!

    A public-private testing partnership certified that ITER's vacuum components can withstand major seismic events. Making sure the ITER tokamak will be safe in th [...]

    Read more

  • Feeders | Delivering the essentials

    Like a circle of giant syringes all pointing inward, the feeders transport and deliver the essentials to the 10,000-tonne ITER magnet system—that is, electrical [...]

    Read more

  • Image of the week | It's FAB season

    It's FAB season at ITER. Like every year since 2008, the Financial Audit Board (FAB) will proceed with a meticulous audit of the project's finances, siftin [...]

    Read more

  • Disruption mitigation | Final design review is a major step forward

    The generations of physicists, engineers, technicians and other specialists who have worked in nuclear fusion share a common goal, dedication and responsibility [...]

    Read more

  • Image of the week | Like grasping a bowl of cereal

    Contrary to the vast majority of ITER machine components, the modules that form the central solenoid cannot be lifted by way of hooks and attachments. The 110-t [...]

    Read more

Of Interest

See archived entries

Latest tests show positive conductor performance

The assembled conductor sample CSIO ready for testing at the Sultan Test Facility. Photo courtesy (2): EPFL-CRPP (Click to view larger version...)
The assembled conductor sample CSIO ready for testing at the Sultan Test Facility. Photo courtesy (2): EPFL-CRPP
The performance degradation problem that was found in a conductor for ITER's central solenoid last year seems to be solved.

As part of a comprehensive R&D program that was launched following unsatisfactory test results, a new conductor was fabricated; recent tests performed at the SULTAN Test Facility in Switzerland show good results. The new conductor sample was submitted to 10,000 magnetic load cycles and two warm-up / cool-down cycles, mimicking one-sixth of the full operational life of ITER's central solenoid.

"Compared to the tests performed last year, the conductor now shows a level of degradation much closer to that originally anticipated in the design, and the rate of degradation with magnetic cycling is stabilizing," explains Neil Mitchell, head of ITER's Magnet Division.

A close-up of the unwrapped cable. (Click to view larger version...)
A close-up of the unwrapped cable.
The tested conductor sample has two new features with respect to previous samples: First, it relies on a different strand manufacturing process, referred to as "internal tin", which has shown good resistance to mechanical bending loads in individual strand tests. Second, it compares two design options: In one, the original cable design is used, with two superconducting strands (copper to non-copper ratio 1:1.0) and one copper strand forming the triplet that is the basis of the cable structure. In the other, three superconducting strands (copper to non-copper ratio 1:1.5) are used. In this three-superconducting strand option, the loads on individual strands are reduced and extra superconducting material is added.

Proof: The graph showing the degradation behaviour of sample CSIO after ~11 000 cycles. (Click to view larger version...)
Proof: The graph showing the degradation behaviour of sample CSIO after ~11 000 cycles.
The root cause of the problems observed in the original tests is believed to be the high magnetic loads accumulating on the strands in the cable-in-conduit conductor. To maintain a low level of coupling losses in the pulsed conditions required in a central solenoid designed for a tokamak machine such as ITER, the contact between strands needs to be limited. However, the strands also need to be supported transversally to limit bending under the Lorentz load. If the strands deform too much, it can lead to gradual fracture of the brittle superconducting filaments and degradation in superconducting performance.


return to the latest published articles