Building accelerator afterburners with plasma.

Particle colliders are pushing the limits of economic and political feasibility. Already, the next generation of planned linear colliders is tens of kilometers long; a planned circular collider is 100 kilometers in circumference. Such massive projects will take years to build and strain government purse strings. And yet, scientists are intent on pursuing even higher energies to reveal more of the universe’s secrets by smashing together fundamental particles. Unable to increase the size of their machines much more, scientists are turning to alternate particleaccelerating methods. Among them is plasma wakefield acceleration, an approach that has shown particular promise in recent experiments. The results suggest that plasma wakefield acceleration could serve as an energy booster to a linear collider, doubling collision energies from 500 gigaelectronvolts to 1 teraelectronvolt, thus allowing much higher energies in the same distance. Although these experimental results unexpectedly stretched the limits of what the best-available simulations had predicted, big technological hurdles remain before plasma wakefield-based devices are ready for prime time. “We’re not trying to save a factor of two in size,” says Mark Hogan, head of the plasma acceleration group at SLAC National Accelerator Laboratory. “We’re really trying to make improvements that are thousands of times better.”