ITER is a world of massive components as tall as buildings and as heavy as commercial aircrafts. Manufactured in different parts of the world, often transported over enormous distances to the ITER construction site, they must be assembled and positioned with utmost precision. The challenge is especially critical when it comes to assembling some of the largest and heaviest machine components into the "sub-assemblies" that form the basic building blocks of the machine.
The four major components of the first building block of the ITER plasma chamber are now aligned (here, a view of the vacuum vessel taken from inside the sub-assembly). This major achievement smooths the way for the similar assembly of eight other sub-assemblies in the months and years ahead.
On 17 September, the assembly teams were able to confirm that the alignment of the four major components—the vacuum vessel sector, its thermal shield, and two toroidal field coils—had been achieved within 0.14 mm of tolerance in the radial direction, 0.25 mm of tolerance in the toroidal direction, and 0.58 mm of tolerance in the vertical direction—"a spectacular result" according to Chang Ho.
Chang Ho Choi, the head of the ITER Sector Modules Delivery & Assembly Division, has moved his office into a small room near the assembly tools. As minute adjustments still need to be performed, his permanent presence is required.
The preparation of the first sub-assembly is now entering its final phase. Once the sleeves are custom machined and positioned, the installation of the intercoil structures will begin. Several other activities (pipe welding for the divertor cooling system and in-vessel viewing system, the installation of small segments of thermal shield, etc.) will be performed simultaneously.
This image shows how the three elements of the sub-assembly are positioned relative to one another. To the right, the bottom part of one of the toroidal field coils (TF13); in the centre, the much thinner silver-plated thermal shield; and to the left, the opening of the vacuum vessel sector lower port stub extension.