Fermi National Accelerator Laboratory
This is a view of the tunnel which comprises the 'Main Ring.' The proton beam travels in a vacuum tube 2 inches by 5 inches located in the center of 1,014 magnets which bend and focus the beam as it travels around the four-mile ring 50,000 times per second. On each revolution, the beam is given a 2.8 million electron volt 'kick' by the radio frequency system, elevating energy to 200 billion electron volts (BeV) or higher. The machine operates regularly at 400 BeV, and has been accelerated to 500 BeV. Cooling water passes through the pipes above, and at the end of the magnets.