Physicists use particle accelerators to answer some of the most profound questions about the nature of the universe. These gargantuan machines accelerate charged particles to nearly the speed of light and then smash them together, re-creating the conditions that existed when our universe was cataclysmically born in the big bang. By analyzing the debris of the collisions, physicists hope to understand how the seemingly disparate forces and particles that exist in our universe are all connected and described by a unified theory. Unfortunately, as they get closer and closer to solving this mystery of creation, physicists need particle accelerators of ever greater power (and expense).
The most powerful particle accelerator, now under construction at CERN, the European laboratory for particle physics on the French-Swiss border, is the 8.6-kilometer-diameter Large Hadron Collider (LHC). After the LHC is completed in 2007, the collisions of its two seven-trillion-volt proton beams should tell us what gives particles their mass [see "The Mysteries of Mass," by Gordon Kane; Scientific American, July 2005]. Other currently operating machines are attempting to explain why the universe contains more matter than antimatter and are giving us a peek into the primordial state of matter called a quark-gluon plasma. All these colliders are based on a bulky decades-old technology in which microwaves accelerate the particles.
Chandrashekhar Joshi is a Distinguished Professor of Electrical Engineering at the University of California, Los Angeles, where he leads the Laser-Plasma Group. He is a recipient of the American Physical Society's James Clerk Maxwell Prize for plasma physics. Credit: Nick Higgins