The Final Focus Test Beam (FFTB) enters its final days this winter. Starting April 10, SLAC will turn off beam to the facility and begin its removal to make way for construction of the Beam Transport Hall (BTH) for the Linac Coherent Light Source (LCLS).

The 200-meter beamline runs from the Beam Switch Yard at the end of the two-mile linac out into the Research Yard. About 100 meters are underground, and the remainder is visible as a long concrete building.

A bird’s eye view of the Research Yard shows the Final Focus Test Beam (shaded), which will be removed to make way for the Beam Transport Hall (dashed lines) of the Linac Coherent Light Source. (Image courtesy of Heather Rock Woods)

The FFTB was originally built to demonstrate technology for focusing and measuring sub-micron electron beams suitable for a future linear collider. Thanks to its small beam emittance and ultra-short electron bunches, it became a microcosm of SLAC, hosting experiments in astrophysics, photon science and cutting-edge accelerator research. Experimenters are currently logging as much beam time as possible before the facility shuts down.

Come 7 a.m. on April 10, phase one of the removal project begins. The Accelerator Systems Division will secure the facility for component removal, with an emphasis on preserving as many components as possible. Carefully considering safety issues, crews will work systematically to identify components and then disconnect electrical, water and protection systems for the FFTB with minimal interference to ongoing linac operations. Researchers will come in during phase one to remove their experimental equipment.

Phase two will begin May 1 under the direction of the LCLS Construction Directorate. A professional rigging subcontractor will remove all remaining items. That includes about 3,000 tons of concrete shielding (some individual pieces are 60-feet long and weigh 38 tons), support structures and up to 250 magnets. All the magnets will be reused at LCLS or other Lab facilities.