It is one thing to shrink the capacity of the 17-mile Large Hadron Collider at CERN to a tabletop device, but it is another to use the miniature particle accelerator to create an energy gradient 1,000 times greater. Researchers at the Lawrence Berkeley National Laboratory have managed to accomplish both, as report Monday in the journal Physical Review Letters.
The team of scientists aimed a beam of laser light from the Berkeley Lab Laser Accelerator, or BELLA, into a 9-centimeter long tube of plasma measuring in diameter only 500 micrometers. The result was the acceleration of electrons inside the tube to an energy of 4.25 giga-electron volts, creating an energy gradient three orders of magnitude over that of traditional accelerators and setting a new world record for laser-plasma accelerators.
“We’re forcing this laser beam into a 500 micron hole about 14 meters away, ” explained Wilm Leemans, lead author on the report, in a statement. “The BELLA laser beam has sufficiently high pointing stability to allow us to use it. The laser pulse, which fires once a second, is stable to within a fraction of a percent. With a lot of lasers, this never could have happened.”
The record-shattering energy could not have been produced without the quadrillion watts of power generated by BELLA, which became operational only last year.
“This result requires exquisite control over the laser and the plasma,” says Leemans, whose work in 2006 set the foundation for the latest accomplishment.
The accelerator works by injecting a pulse of laser light into a thin, short, plasma-containing tube, much like a straw. The laser light pulse creates a channel through the plasma along with waves that grab and accelerate electrons to high energy states, similar to how an ocean wave accelerates a surfer riding down its face.
Leemans and his colleagues are shooting for 10 giga-electron volts in the near future, but this will require greater precision in their control of the plasma channel density as the laser light pulse travels through.