Milestone 10-GeV Experiment Shines Light on Laser-Plasma Interactions

The gas jet system has another benefit: resilience. Because the sheet of gas has no parts to break, the technology can scale to very high repetition rates, which the lab is working toward for future particle colliders and applications.

Researchers also showed that their approach made a beam that was “dark current free,” meaning background electrons in the plasma were not unintentionally accelerated.

“If you have dark currents, they’re sucking up the laser energy instead of accelerating your electron beam,” said Jeroen van Tilborg, an ATAP staff scientist and deputy director in charge of BELLA’s experimental program. “We’ve gotten to a point where we can control our accelerator and suppress unwanted effects, so we are making a high-quality beam without wasting energy. That’s essential as we think about the ideal laser accelerator of the future.”

The technology has a wide range of potential applications. For example, it could be used to produce particle beams for cancer treatments. Or it could power free-electron lasers that act like atomic microscopes, helping to create advanced materials and gain insight into chemical and biological processes.

“We’ve taken a big step towards enabling applications of these compact accelerators,” said Anthony Gonsalves, an ATAP staff scientist who leads accelerator work at BELLA. “For me, the beauty of this result is we’ve taken away restrictions on the plasma shape that limited efficiency and beam quality. We have built a platform from which we can make big improvements, and are poised to realize the amazing potential of laser-plasma accelerators.”

Scaled up to higher energies, laser-plasma accelerators could have applications in fundamental physics and beyond. In the near-term, LPAs could be used to produce beams of muons that help image difficult-to-explore areas, including architectural structures like ancient pyramids, geologic features like volcanoes or mineral deposits, or the interior of nuclear reactors. On a longer scale, the technology could power higher-energy particle colliders that smash charged particles together, searching for new particles and deeper insights into the forces underlying our universe. Researchers at BELLA are now working on developing these very high energy machines by connecting the building blocks together in a staged accelerator system.

“Coupling stages together gives us a realistic path to generate electrons between 10 and 100 GeV, and to build toward future particle colliders that can reach 10 TeV [teraelectronvolts],” said Eric Esarey, director of the BELLA Center. “Once the laser energy from one stage is depleted, we send in a new laser pulse, boosting the electron energy from stage to stage in series.”

To create staged systems, it’s essential that researchers have good diagnostics. This lets them understand how the plasma, laser, and electron beam are behaving, and gives them precision control over the timing and synchronization of steps happening in the barest fraction of a second.

“With this study, we’ve advanced the particle energy of high-quality beams in very short distances, and the efficiency with which we can make them, by using precision diagnostics that give us great laser-plasma control,” said Cameron Geddes, director of Berkeley Lab’s ATAP Division. “Advancing laser-plasma accelerator technology has been identified as an important goal by both the U.S. Particle Physics Project Prioritization Panel (P5) and the Department of Energy’s Advanced Accelerator Development Strategy. This result is a milestone on our way to staged accelerators that are going to change the way we do our science.”

This work was supported by the Department of Energy’s Office of Science, Office of High Energy Physics, and the Defense Advanced Research Projects Agency, and used the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science user facility.

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