In one corner of the ITER Assembly Hall, work has started on the second of the six modules. Once all six are stacked one on top of another, they will form the 18-metre-tall, 1,000-tonne ITER central solenoid.
Whether in the Tokamak assembly pit, in one of the twin sub-assembly tools or in any support or transport structure, the positioning of a component requires both heavy machinery and subtle adjustment devices. This is particularly true of the central solenoid modules: as the approximately 2-metre-tall components are stacked upon one another, any deviation from nominal would be progressively amplified as the stacking progresses. And the tolerance for deviation is low: no more than 20 mm for the 18-metre-tall structure once completed.
It takes a whole range of tools to position the 110-tonne component with the required precision: once cranes and ''synch hoists'' have done the heavy job, a complex system of subtle adjustment devices allows micrometric movements in pitch, roll and spin.
Stacking cylindrical devices and connecting their fragile electrical and cryogenics leads demands a particular attention to concentricity and straightness. "We have a target of concentricity between two cylinders of about 0.2 mm and the same for straightness (0.2 mm over 350 mm)," says Carl Cormany, the superconductor engineer responsible for central solenoid assembly. Such precision is achieved through a complex system of adjustment devices whose manual handles allow micrometric movements in pitch, roll and spin.
''In terms of precision, nothing is trivial,'' says Carl Cormany, the superconductor engineer responsible for central solenoid assembly. He is seen here standing on top of the scaffolding that gives access to the inside of the module.
For operations as strategic as installing ITER components and systems, precision is taken into account long before platforms and tooling are installed. "In terms of precision, nothing is trivial," specifies Cormany. "The formulation of the concrete that anchors the platform plays a part, as does the way bolts are tightened." For a specialist in superconductivity, this is a new domain of expertise.
