The linear accelerator and SPEAR3 can work through the heat. A number of upgrades and the outstanding work of the maintenance staff have kept the beams operational for the great majority of Northern California's recent heat wave.
"It's only on the very hottest days that it's a problem," said Roger Erickson, who manages accelerator operations at SLAC.
During the peak of the heat wave on July 22 and 23, when temperatures exceeded 100 degrees Fahrenheit, both accelerators struggled as equipment overheated. Dozens of problems appeared for the linac, keeping the beams off until late in the evenings. SPEAR3 avoided losing beam.
"Many of the maintenance workers made heroic efforts, working in hot and uncomfortable areas around the site to help restore operations," said Erickson.
The machines are typically shut down for maintenance and upgrades in the late summer, when power costs are higher and heat waves more likely. This year, the linac and PEP-II will run until August 21 and SPEAR3 will shut down on August 7.
Twenty-five feet below ground, the linac itself stays a constant 113 degrees, a perfectly comfortable temperature for the electrons, positrons, magnets and accelerator structures. However, the components above ground can suffer in high ambient temperatures. Electronics and power supplies are especially vulnerable and can trip off. The heat also causes problems with the control system and high power components at the above-ground SPEAR3.
"We are actively upgrading our air conditioning systems this summer for the SPEAR accelerator complex, not just to handle the hot weather, but also to improve beam stability," said Bob Hettel, head of the SSRL Accelerator Systems Department.
During the summer, Erickson gets email alerts from power company PG&E requesting voluntary power conservation. After receiving an alert during recent linac maintenance, the operations crew turned off additional equipment "to be good citizens and reduce our power bill," he said.
Heather Rock Woods
Above image: Maintenance on the linac, which operates at a constant 113 degrees Fahrenehit. (Photo courtesy of Peter Ginter. Click on image for larger version).