From “SLAC Today,” http://today.slac.stanford.edu/

The first undulator support girder assembly for the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC) made its way from the Collider Hall, where technicians are piecing them together, to the Magnetic Measurement Facility for final alignment. Each of the 33 girder assemblies [which were designed at the Argonne Advanced Photon Source by the Accelerator Systems Division Mechanical Design and Engineering Group along with Geoff Pile and Marion White, who are attached to the LCLS project] comprises a steel girder, movable supports that position the undulator magnets, a quadrupole magnet, a wire beam scanner, and the vacuum chamber that carries the beam.

"This is an exciting point in the assembly," said Eric Lundahl (SLAC), team leader of the measurement group making the adjustments. "The next step is the marriage of an undulator, and then we have our first undulator–girder assembly."

The girders and associated components must be aligned to very tight tolerances for the LCLS to work properly. The vacuum chamber—an aluminum pipe that carries the beam through the undulator magnet—is a mere 6 millimeters thick. The gap in the undulator where it fits, by contrast, is only 6.8 millimeters, a difference amounting to a few ten-thousandths of an inch. However, the straightness of the beam pipe can only vary by tens of microns, making the undulator gap tolerance look huge by comparison.

Technicians plan to test-fit undulators to the girders during the tuning phase in the MMF, but the final assembly will take place in the Undulator Hall (UH). Together, the 5,500 pound girder and undulator will rest atop support stands that are currently awaiting installation in the UH tunnel.

The LCLS is a collaboration of laboratories from across the United States. Argonne managed the design and manufacture of the undulator magnets, vacuum chambers, support stands, girders and associated equipment. –Brad Plummer (SLAC)