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News & Media

Latest ITER Newsline

  • Upper ports | A very international effort

    The 18 upper ports of the ITER vacuum vessel are procured by Russia, manufactured in Germany, and mounted (in part) on the vessel sectors by contractors in Ital [...]

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  • Paint job | One level done, five to go

    The job is done and the effect is spectacular. At the deepest basement level (B2) of the Tokamak Building, the floors, walls, and ceilings are now perfectly whi [...]

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  • On site | Through the eyes of a crane operator

    Sitting in his cabin 80 metres above the ground, Alex Dumonteil enjoys a most spectacular view. To the north, on a clear day, he can see as far as the Alpine ri [...]

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  • Poloidal field coil #6 | The home stretch

    In Hefei, China, a 400-tonne ring magnet procured by the European Domestic Agency is entering the final phase of production—resin impregnation. In just over one [...]

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  • Neutral Beam Test Facility | SPIDER gets a beam for its first birthday

    Just one year ago, on 11 June 2018, the world's largest negative ion source was inaugurated at the ITER Neutral Beam Test Facility with the ignition of a brief [...]

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Of Interest

See archived entries

Of mega tools and dentist drills

R.A.

The Poloidal Field Coils Winding Facility, where conductor lengths are transformed into large ring-shaped magnets, is the realm of large and powerful tools: tower-like "de-spoolers", a 5-metre-high vacuum test chamber, winding tables that are 17 metres in diameter, and an impregnation station as big as a carousel.

 (Click to view larger version...)
Much less visible but no less important to the fabrication process is a humble drill, barely larger than one a dentist might use.

Operated by hand, the drill is used to finalize so-called "penetrations"—openings by which liquid helium will flow into the cable-in-conduit conductor.

The operation is an extremely delicate one. First, a larger power drill is used to carefully bore a one-euro-size hole into the conductor's steel jacket. Then—using a small hand drill—the technician advances by one-tenth-of-a-millimetre increments until steel foil is exposed. (The foil, only two-tenths of a millimetre thick, is wrapped around the superconducting strands inside the conductor).

Throughout the operation the inside of the conductor is placed under pressure so that all metal particles generated by the drill are evacuated. And as a side benefit, the pressure results in a "hissing" sound as soon as the steel foil is pierced, effectively warning the technician to be extra cautious.

Because it is of vital importance that the superconducting strands remain unharmed, the technician wields the drill carefully in the final stage of the process to slowly and progressively chip away at the steel foil until the strands are exposed.

The French company CNIM has been chosen by Europe as the manufacturing contractor in the Poloidal Field Coils Winding Facility, where four of ITER's poloidal field coils will be fabricated.

Employees from CNIM have been practising the drilling technique for a few weeks now, and report that they feel comfortable with it. "Two tenths of a millimetre? That is a very comfortable safety margin," smiles André Forestier, the company's foreman on the ITER site.

In the long and complex sequence of operations that transforms conductor lengths into poloidal field coils weighing up to 400 tonnes, the quality of the hand drilling job is crucial. Once equipped with a helium inlet, each penetration (eight per coil, on average) forms a most strategic interface between the cryogenic system and the coils.


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