Researchers Announce Record for Plasma Accelerator Operation

A team of researchers at Deutsches Elektronen-Synchrotron (DESY) has run a laser plasma accelerator for more than a day while continuously producing electron beams. The LUX beamline, jointly operated and developed by DESY and the University of Hamburg, achieved a runtime of 30 hr.

“This brings us a big step closer to the steady operation of this innovative particle accelerator technology,” said Andreas R. Maier, who leads the group.

During the record-breaking nonstop operation, the physicists accelerated more than 100,000 electron bunches, one every second. With that large data set, the properties of the accelerator, the laser, and the bunches can be correlated and analyzed more precisely.

In laser-plasma acceleration, a strong laser pulse (red) generates a plasma wave (blue) in hydrogen gas by stripping electrons from gas molecules. The electrons (red) ride the wave like a surfer in the wake of a boat. This pushes them to high energies extremely quickly. The LUX facility has now continuously delivered more than 100,000 of these particle bunches in around 30 hr. Courtesy of DESY, Science Communication Lab.

“Unwanted variations in the electron beam can be traced back to specific points in the laser, for example, so that we know exactly where we need to start in order to produce an even better particle beam,” Maier said.

“This approach lays the foundations for an active stabilization of the beams, such as is deployed on every high-performance accelerator in the world,” said Wim Leemans, director of DESY's Accelerator Division.

According to Maier, the key to success was combining expertise from two different fields: plasma acceleration and know-how in stable accelerator operations. Both are available at DESY. A number of factors contributed to the accelerator's stable operation, including vacuum technology and laser expertise, as well as a comprehensive and sophisticated control system.

“In principle, the system could have kept running for even longer, but we stopped it after 30 hours,” Maier said. “Since then, we have repeated such runs three more times.”

The accelerator uses a laser or energetic particle beam to create a plasma wave inside a fine capillary. Within the capillary is hydrogen gas. The laser or particle beam is used to strip away the electrons, creating the plasma.

“The laser pulses plow their way through the gas in the form of narrow discs, stripping the electrons from the hydrogen molecules and sweeping them aside like a snowplow,” Maier said. “Electrons in the wake of the pulse are accelerated by the positively charged plasma wave in front of them — much like a wakeboarder rides the wave behind the stern of a boat.”

This phenomenon allows laser plasma accelerators to achieve acceleration strengths that are up to 1000× greater than what could be provided by today’s most powerful machines. Plasma accelerators will enable more compact and powerful systems for a wide range of applications, from fundamental research to medicine. A number of technical challenges still need to be overcome before these devices can be put to practical use.

The research was published in Physical Review X (www.doi.org/10.1103/PhysRevX.10.031039).