UCLA and SLAC Develop Plasma Accelerator that Boosts Electron Beam Energy and Quality Simultaneously
The advance could pave the way for new scientific cameras and microscopes capable of probing nature’s fastest motions and smallest building blocks
Greg Stewart/SLAC National Accelerator Laboratory
In a plasma wakefield accelerator, a high-energy drive beam (right, larger yellow-green oval) creates a plasma wake “bubble” (center, green oval) where a new, denser electron bunch (left, smaller yellow oval) forms.
UCLA Samueli Newsroom
A team led by researchers from the UCLA Samueli School of Engineering and the U.S. Department of Energy’s SLAC National Accelerator Laboratory has shown that a plasma accelerator can transform a state-of-the-art electron beam into one that is simultaneously much brighter and higher in energy.
Published Nov. 28 in Nature Communications, the breakthrough lays the foundation for compact X-ray lasers — ultra-powerful cameras that can capture images of atoms in motion in freeze frame. The advance could also help significantly reduce the size of future particle colliders, which act as “super microscopes” for exploring nature’s fundamental building blocks.
The study’s co-corresponding authors are Chan Joshi, a distinguished professor of electrical and computer engineering and Chaojie Zhang, a UCLA Samueli associate project scientist. Mark Hogan, director for SLAC’s Facility for Advanced Accelerator Experimental Tests, where the experiments were conducted, is also a co-author. Additional contributors include researchers from UCLA Samueli’s Department of Electrical and Computer Engineering, UCLA Department of Physics and Astronomy, SLAC, the University of Oslo in Norway, the Institut Polytechnique de Paris in France and the University of Colorado Boulder.
In the experiment, researchers sent a 10-giga-electronvolt beam (10 billion volts of energy gained by an electron) into a meter-scale column of hydrogen gas. This beam, which had already accelerated by a kilometer-long conventional accelerator, was so intense that it ripped the hydrogen atoms apart into a plasma — a hot gas of electrons and ions. The initial “drive beam” created a near light-speed wake in the plasma, similar to the trail left by a speedboat. Electrons in the plasma were then trapped and further accelerated in that wakefield to energies of up to 26 GeV. The entire process unfolded in just two meters.
The new beam was up to 38 times brighter, higher in energy, more densely packed and more tightly focused than the original beam. While the original output is like a powerful floodlight, the new beam behaves like a laser pointer, concentrating its energy into a single tiny and parallel beam. This combination of brightness and sharp focus is essential for many scientific applications.
In the near future, this bright electron beam could power compact X-ray free-electron lasers — devices that pulse for a millionth of a billionth of a second, fast enough to capture individual atoms and molecules at a standstill during chemical reactions. Brighter, more compact X-ray lasers could also help scientists reveal molecular dynamics in unprecedented detail, leading to breakthroughs in medicine, new quantum materials and battery technology.
Over the long term, these super microscopes could collide particles to probe nature’s fundamental building blocks. The advance could also enable the development of smaller, more cost-effective high-energy particle colliders, helping to overcome the challenges posed by the massive, expensive facilities required by current technology.
SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science, which funded the research.