Hole in one: Technicians smoothly install the center stack in the NSTX-U vacuum vessel
By John Greenwald
November 10, 2014
With near-surgical precision, PPPL technicians hoisted the 29,000-pound center stack for the National Spherical Torus Experiment-Upgrade (NSTX-U) over a 20-foot wall and lowered it into the vacuum vessel of the fusion facility. The smooth operation on Oct. 24 capped more than two years of construction of the center stack, which houses the bundle of magnetic coils that form the heart of the $94 million upgrade.
“This was really a watershed moment,” said Mike Williams, the head of engineering and infrastructure at PPPL and associate director of the Laboratory. “The critical path [or key sequence of steps for the upgrade] was fabrication of the magnets, and that has now been done.”
The lift team conducted the final steps largely in silence, attaching the bundled coils in their casing to an overhead crane and guiding the 21 foot-long center stack into place. The clearances were tiny: The bottom of the casing passed just inches over the shielding wall and the top of the vacuum vessel. Inserting the center stack into the vessel was like threading a needle, since the clearance at the opening…