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The FACET facility will involve relocation, refurbishment and upgrading of accelerator components at SLAC to provide beams at a new facility in Sector 20 of the SLAC linac. The goal of the FACET facility is to deliver high quality beams for plasma wakefield accelerator research. The facility will be located upstream of the injector for SLAC's Linac Coherent Light Source, as illustrated in the figure below. It will use the upstream two kilometers of the SLAC linac and a new experimental area at Sector 20 in the existing linac tunnel.
By installing a new focusing system at Sector 20, the SLAC linac electron beam can be focused and compressed in length to sizes appropriate for plasma wakefield accelerator research. Comparable power densities for positron beams will be provided with the addition of an upstream positron bunch compressor in Sector 10. A shielding wall at the end of Sector 20 will allow access to the upstream portion of the linac during LCLS operations.
The FACET facility features six main components:
FACET will rebuild the beamline in the sector 20 region of the linac tunnel to compress and focus the beam to less than 100 femtoseconds in duration to less than 10 microns transversely. An additional 30 meters of beamline provides a general purpose experimental area with facilities for mounting experiments and safely dumping the beam. Experimenters will access the tunnel through a new staircase located in sector 19 and shown in green.
In 2002 a magnetic chicane was added to sector 10 of the main linac to compress electron bunches. The beam is accelerated to the chicane in such a way that when it arrives, the particles in the head of the bunch have a lower energy than those in the back. When the particles travel through the curved trajectories of the chicane, the high energy particles take a shorter path and catch up to particles in the head, compressing the bunch. Since magnets deflect electrons and positrons in opposite directions, FACET will upgrade the chicane in early 2012 by adding additional magnets, providing compressed positron bunches for the first time.
SLAC National Accelerator Laboratory, Menlo Park, CA
Operated by Stanford University for the U.S. Dept. of Energy