Klystron gallery of SLAC linear accelerator. The power to accelerate electrons along the 3.2 km (2 mile) linear accelerator at the Stanford Linear Accelerator Center (SLAC), California, comes from devices called klystrons. These powerful sources of radio waves (in fact, microwaves) are installed in the 'klystron gallery' that runs along the surface, 8 metres above the accelerator itself. The klystrons, the structures with red cylinders, are about 12 metres apart. SLAC is one of the world's leading particle physics laboratories. The photograph was taken in 1994.