Valuable Real Estate in the Research Yard
This is land the Final Focus Test Beam (FFTB) occupied for 13 years, starting underground where the linac ends and emerging through the giant concrete wall into the Research Yard.
It's the original home of Beam Line C and End Station C, which ran straight from the linac between End Station A and End Station B (where the owls have been nesting). End Station C was not a giant edifice like its neighbors, but was formed from stacked concrete blocks which shielded the beam line. A 42-inch bubble chamber was hidden inside. End Station C was taken apart in 1990 to make way for the FFTB, just as the FFTB is now being removed to make way for the Linac Coherent Light Source.
This patch of ground does not like to hold still, literally or figuratively.
"The Research Yard floor moves out toward End Station B in the morning as the sun rises and heats it up, and then comes back toward End Station A as it cools," said Dieter Walz, who's been involved with the FFTB from planning through the final days of beam this month.
Had the millimeter-scale daily migrations of the earth gone unchecked, magnets would have moved off-center from the beam and ruined focusing efforts. To minimize migration, crews cut grooves through the FFTB floor and supported magnets and some instruments on monuments sunk deep below the concrete floor. In addition, the thick concrete ceiling and walls minimized the sun's exposure.
To protect researchers from radiation, a 54-foot-long steel shield was placed between the Beam Switch Yard at the end of the linac and the beginning of the FFTB. That same shield will now protect the crews that are removing FFTB equipment while BaBar keeps running.
This summer, you can watch as the newest facility to use this territory takes shape. Construction crews will take away the FFTB concrete housing, and begin building the Beam Transport Hall for the LCLS.
Image: Workers began dismantling the FFTB this week. (Click on image for larger version.)
Heather Rock Woods SLAC Today, April 13, 2006