Quark Science Powers FEL (SPACE.com)
Quark Science Powers FEL
By James Schultz, SPACE.com
Jefferson Laboratory is a $600 million nuclear physics research facility built around the world's first large-scale superconducting electron accelerator — a complex assembly of high-tech hardware and electronics stretching through an underground tunnel almost a mile (1.6 kilometers) in circumference. Delivering a continuous beam of electrons to a target substance like hydrogen, carbon, gold or lead, the accelerator enables physicists to study quarks — subatomic particles thought by most scientists to be nature’s fundamental building blocks.
The accelerator uses superconducting radio-frequency technology to drive electrons to higher and higher energies. Pushed to light speed by radio waves, the electron beam travels around the tunnel five times in twenty four-millionths of a second. As the beam collides with the target, particles scatter. By studying the speed, direction and energy of the quarks and other particles, scientists learn more about how protons and neutrons in the atom's nucleus fit together and interact.
The FEL, or free-electron laser, apparatus is a smaller version of the accelerator. Like its fraternal twin, the FEL accelerator takes individual electrons stripped from a source material and injects them into a racetrack-like oval. By the time the electrons reach a device known as a "wiggler," they are highly energized. Inside the wiggler, magnets bounce the electrons back and forth &8212; like ping-pong balls bouncing off the paddles of opposing players. The back-and-forth movement further increases the electrons’ energy, which is subsequently released as laser light.