August 19, 2005  


SPEAR3 Beam Lines Undergo Upgrades During Downtime

Close-up of SPEAR3.
(Photo by Peter Ginter)

By Heather Rock Woods

Three beam lines on the SPEAR3 accelerator are undergoing major upgrades during the machine’s scheduled downtime that started August 1 and ends November 28. A large number of SLAC staff members from many different groups is contributing to the effort.

When operations resume, beam lines 9 and 10 will be ready to handle the fivefold increase in beam power—to 500 milliamps (mA)—that SPEAR3 began generating on June 20. The beam line development team will commission beam line 7 starting in January 2006.

SSRL currently has 11 beam lines; 18 experimental stations operated during the recent run. A typical beam line carries the x-rays created by magnets on the SPEAR3 storage ring some 30 to 35 meters to experimental stations where the research is done.

Beam line 9 delivers x-rays through three branch lines to three experimental stations. Two stations are for macromolecular crystallography and one is for x-ray absorption spectroscopy of biological systems. The line is funded by the DOE Office of Biological and Environmental Research.

Beam line 10, funded by the DOE Office of Basic Energy Sciences (BES), has two experimental stations. The station for vacuum ultraviolet and soft x-ray studies has been largely upgraded for 500 mA already. The second station, which is the focus of this summer’s activities, is for hard x-ray materials science applications.

The upgrades to beam lines 9 and 10 involve mostly power handling and systems that channel the beam, which will now need additional cooling so the increased beam current does not damage optics or metal components. Meanwhile, elderly beam line 7 is being almost completely rebuilt.

“We’re in the throes of taking a bulldozer to beam line 7 to scrape it clean and start over. Between the increased beam current and the new wiggler magnet recently installed, that represents a 15-fold increase in the power of the beam, which was too much for the old beam line,” said Tom Rabedeau (ESRD), head of beam line development.

The National Institutes of Health (NIH) is funding two stations at beam line 7: macromolecular crystallography and biological x-ray absorption spectroscopy. The third station, used for materials scattering, is receiving funds from BES.

In addition to the three major upgrades, SSRL is doing more minor work on four other beam lines, and designing and fabricating two brand new lines that will be installed during the 2006 downtime. Beam line 12, privately funded by the Moore Foundation through Caltech, will allow study of very small macromolecular crystallography samples. Beam line 13, for vacuum ultra-violet and soft x-ray materials science, is being funded by BES.

“We’re in the middle of a three-ring circus of design, fabrication and installation,” said Rabedeau.





The Stanford Linear Accelerator Center is managed by Stanford University for the US Department of Energy

Last update Friday August 19, 2005 by Chip Dalby