The magnet girder displayed for Summer Sunday visitors on July 24 is the first of 90 multipole girders that the Accelerator Division is installing in the NSLS-II storage ring. Also coming are 60 dipole girders and 13 insertion devices. The march of magnets and insertion devices, themselves made up of an array of magnets, will continue around the storage ring until December 2012.
According to Lewis Doom, project engineer in charge of magnet girder assembly, each 12-foot-long multipole girder consists of a rigid structure supporting a series of magnets that surround a vacuum chamber. Three types of magnets are part of the girder assembly:
The magnets are very accurately positioned on the girder, with each placed within 30 microns of its ideal location. “Thirty microns is about the thickness of a sheet of aluminum foil,” said Doom. Each girder will be located in the storage ring tunnel within 100 microns of its ideal location.
What visitors did not see on Summer Sunday was the equally exacting process used to move the girder from Bldg. 902, where assembly takes place, into the NSLS-II storage ring.
As described by Greg Fries, project engineer in charge of installation, the journey begins with the Lab’s riggers, who use an overhead crane to load the 20,000-pound girder onto a flatbed truck. The riggers drive the girder to the ring building entrance and use a large forklift to move it from the truck onto a set of “tall” dollies.
At that point, the division’s mechanical techs take over. Using a ride-on electric “tugger,” they pull the loaded dollies across the experimental floor to a storage-ring entrance, where a pair of “short” air casters awaits. Because the floor of the ring tunnel sits eight inches higher than the experimental floor, the girder has to be transferred into the tunnel to the air casters, which then float the girder to its proper position.
“We've only done this move twice, so it is far from routine,” said Fries. “The process is still being optimized by Frank Lincoln and our mechanical technicians.”
Here’s one thing they’ve learned: The floor needs to be very clean for the heavy girder to roll on the dollies. Said Fries, “We sweep the floor just before with a very fine-bristled broom.”
— Mona S. Rowe, Photon Sciences Communications Manager