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Surfing for Granite

(Photo - Granite block)The Linac Coherent Light Source (LCLS) project is a collaboration that brings together components and equipment from dozens of suppliers. Last month, joined that supply chain. Ed Akerstrom, a member of the LCLS undulator assembly team, scored a huge find—a six-ton block of granite—on the popular website and saved SLAC thousands of dollars in the process.

Akerstrom, a machinist who regularly trolls for deals on tools, found the 15-foot-long granite block by accident. Coincidentally, the seller was associated with a previous SLAC-approved supplier, making acquisition of the stone a lot easier.

"He told me about his find on the phone," said Ben Poling, the undulator assembly team leader. "When he said they only wanted $300 for it, I figured he must have the dimensions wrong."

Granite blocks of this size provide solid, ultra-stable platforms for mounting sensitive equipment. The team, now working in the Collider Hall, had been searching for such a block to use as part of a production line for pre-setting the beam pipe vacuum chambers before they are mounted to the undulator assemblies. Since its arrival, the block has been milled to surface precision that varies less than half of one thousandth of an inch, achieving what Poling terms "AA grade." A stone of this size and quality normally would cost more than $15,000, but thanks to Akerstrom's online acumen, the group spent a fraction of that.

"It cost more to have the stone trucked over to SLAC," said Poling. Once it was finished, the total cost of shipping, mounting and resurfacing was less than $3000, according to Poling.

With the new granite block in place, the assembly team can soon start piecing together the associated structures that will hold the undulator magnets. These massive assemblies will comprise 33 undulators divided among 11 individual cells made up of heavy support pedestals, quadrupole focusing magnets, beam position monitors and related components.

The LCLS is designed such that many of its key systems, including the undulator magnets, can be fine-tuned as necessary without having to take down the machine. Recently, another key component in this fine-tuning system began arriving at SLAC. Called undulator support movers, these devices contain high-precision motors that can make minute adjustments on the fly to keep the undulators aligned to within a few microns.

With a stream of such key components arriving by the week, the undulator assembly team will soon be ready to begin piecing together the undulator assemblies in advance of installation, scheduled to begin next year.

Brad Plummer, SLAC Today, October 23, 2007

Above image: Ben Poling (left) and Ed Akerstrom with the six-ton granite block Akerstrom acquired on Craigslist. (Click on image for larger version.)