Image of the week
Adjusting a correction coil's position
Compared to the massive ITER magnets that weigh up to 400 tonnes, the machine's correction coils are quite lightweight: at 4.5 tonnes, they are the smallest of the superconducting magnetic system. Distributed around the machine in three sets of six (top, bottom and side), they are tasked with reducing the minute deviations of the magnetic field caused by imperfections in the position and geometry of the toroidal and poloidal field coils. Based on a build-to-print design developed by the ITER Organization, they are the procurement responsibility of the Chinese Domestic Agency and its contractor ASIPP (Institute of Plasma Physics, Chinese Academy of Sciences).
The first bottom correction coil (BCC/4) was installed in the assembly pit on 21 October 2021, followed five days later by BCC/5. The correction coils must be precisely positioned in a very restricted space between poloidal field coils #5 and #6, lower magnet feeders, and staging platforms. Depending on the coil, the "room to move" is in the range of 15 to 25 mm.
Workers from the CNPE Consortium are seen here carrying out metrology measurements and adjusting the kidney-shaped coil's position on its yellow temporary supports.
Facing similar constraints, a third kidney-shaped bottom correction coil (BCC/6) was successfully installed on 5 January. Workers from the CNPE Consortium (Tokamak assembly contractor TAC/1) are seen here carrying out metrology measurements and adjusting the coil's position on its yellow temporary supports (final positioning will be possible only when all vacuum vessel modules are in place). A fourth bottom correction coil (BCC/3) is scheduled for installation this week, while the full set of six should be in place by the end of February.
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