Subscribe options

Select your newsletters:


Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Open Doors Day | An intense and unforgettable experience

    Saturday was Jacques's birthday. At age 90, the long-retired engineer from Aix-en-Provence had only one item on his wish list: to visit ITER for a third time an [...]

    Read more

  • Power conversion | A potent illustration of the "One ITER" spirit

    Europe made the buildings; the piping came from India; China and Korea provided the transformers; Russia manufactured the massive 'busbar' network. The ITER Org [...]

    Read more

  • Fusion world | Upgrade completed on DIII-D tokamak

    The DIII-D National Fusion Program (US) has completed a series of important enhancements to its fusion facility, providing researchers with several first-of-a-k [...]

    Read more

  • Vacuum lab | Ensuring leak test sensitivity

    A helium leak test is one of several factory acceptance tests planned for the sectors of the ITER vacuum vessel before they are shipped to ITER. In a vacuum lab [...]

    Read more

  • Bookmark | The Future of Fusion Energy

    To write about fusion is to walk a fine line between the temptation of lyricism and the arid demands of scientific accuracy. Whereas the general media tends to [...]

    Read more

Of Interest

See archived entries

Correction coils

Closing the case

Krista Dulon

Over the past six years, the Chinese institute responsible for the fabrication of ITER's 18 correction coils has successively qualified the winding, impregnation, case manufacturing and assembly steps. A final review carried out in August on the closure welding of the casing completes process qualification activities, allowing the first production coil to be finalized this year.

A high-power laser weld system has been specially developed by ASIPP contractors to seal the structural case of each correction coil. (Click to view larger version...)
A high-power laser weld system has been specially developed by ASIPP contractors to seal the structural case of each correction coil.
In a spacious workshop at the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP), sparks fly as a welding robot makes a pass along the top edge of a full-scale bottom correction coil prototype. Designed to negotiate the unusual shape of the correction coils—which are either banana-shaped (top and bottom coils) or non-planar squares (side coils)—the robot is using autogeneous laser welding to perform the last in a series of qualification activities: final closure welding.

"This last step is a delicate one," explains Fabrice Simon from ITER's Magnet Division. "At this point the superconducting winding pack has been inserted into its steel case and the top lid must be welded shut. The technical specifications demand gap tolerances of less than 0.3 mm, which means a tight tolerance machining of both case and lid over the total 30 metres of weld as well as the control of welding shrinkage. The ASIPP took up the challenge with enthusiasm, and developed a 'skip and balance' welding sequence that has proven successful, with the robots welding opposite corners, then opposite sides to balance the shrinkage effect."

A ''dummy'' superconducting winding pack is inserted into a prototype steel case. The last qualification step—laser closure welding—was performed at ASIPP in June/July and the results were presented during a joint ITER Organization/Chinese Domestic Agency/ASIPP meeting at ITER Headquarters in August. (Click to view larger version...)
A ''dummy'' superconducting winding pack is inserted into a prototype steel case. The last qualification step—laser closure welding—was performed at ASIPP in June/July and the results were presented during a joint ITER Organization/Chinese Domestic Agency/ASIPP meeting at ITER Headquarters in August.
Two robots and powerful 20 kW laser weld tools have been engineered to work over the coils' large surfaces. It took one year to establish the best processes for case closure based on tests run to characterize the welds and ensure mechanical strain properties. The closure weld test on the full-scale prototype case, initiated in June, took approximately two months including inspection and dimensional checks.

Six bottom coils, six side coils and six top coils will be installed around the Tokamak. Their role is to reduce magnetic error fields caused by imperfections in the position and geometry of the principal coils. (Click to view larger version...)
Six bottom coils, six side coils and six top coils will be installed around the Tokamak. Their role is to reduce magnetic error fields caused by imperfections in the position and geometry of the principal coils.
"Weld quality was better than expected and most dimensions met requirements," confirms both Wei Jing, project leader for ASIPP, and Dr Niu, from the Chinese Domestic Agency (ITER China). The ITER Organization, ITER China (responsible for the procurement of the coils), and manufacturer ASIPP discussed the detailed test results at a three-day meeting that took place last week at ITER Headquarters. Once all documents have been signed, the qualification phase for bottom and top correction coil manufacturing officially comes to an end and series production can continue full speed. The last challenge for ASIPP will be to qualify the case closure welding for the side corrections coils, which have bigger and more flexible structures than the bottom correction coils.

At ASIPP, production is underway on the six bottom correction coils—the first set needed for installation at ITER. Teams have completed five winding packs, carried out vacuum pressure impregnation on four, and produced the first case structure. Later this month, the insertion of the first impregnated winding pack into its case is scheduled, to be closely followed by closure welding.

By the end of the year, the first bottom correction coil, BCC #1, will be ready for cold testing.

Click for more information on the qualification of correction coil winding and coil case manufacturing.


return to the latest published articles