Methods used for the first time using the Laser Energy Laboratory’s OMEGA laser system reveal the potential of spark fusion on a larger scale. Researchers at the University of Rochester’s Laser Energy Laboratory (LLE) have conducted experiments demonstrating an effective “spark plug” for direct-drive approaches to fusion (ICF). In the two studies presented journal Nature Physicsteam shares their findings and details the potential to scale up these techniques for successful fusion in a future facility.

LLE is the U.S. Department of Energy’s largest university program and is home to the OMEGA Laser System, which is the world’s largest academic laser but still has nearly one percent lower energy than the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. in California. . Rochester scientists, with help from OMEGA, have made several successful attempts to fire 28 kilojoules of laser energy at small capsules filled with deuterium and tritium fuel; This caused the capsules to explode, producing a plasma hot enough to initiate fusion reactions between the fuel cores. The experiments resulted in fusion reactions that produced more energy than the amount of energy in the central hot plasma.

OMEGA experiments use direct laser illumination of the capsule and differ from the indirect excitation approach used in NIF. When the indirect drive approach is used, the laser light is converted into X-rays, causing the capsule to explode. NIF used an indirect drive to irradiate the capsule with X-rays using approximately 2,000 kilojoules of laser energy. This led to a breakthrough at NIF in 2022 in achieving fusion ignition, a fusion reaction that creates a net gain of energy from the target.

Achievements and prospects

The first paper’s lead author is Connor Williams ’23 Ph.D. “The creation of a fusion energy that exceeds the internal energy of the fusion zone is an important threshold,” he says. (physics and astronomy), currently a full-time scientist at Sandia National Laboratory in the development of radiation and ICF targets. “This is a necessary condition for anything you want to achieve later, such as burning plasma or achieving ignition.”

Having demonstrated that they can achieve this level of burst efficiency with just 28 kilojoules of laser energy, the Rochester team is excited about the possibility of applying direct excitation techniques to higher-energy lasers. Showing the spark plug is an important step, but the OMEGA is too small to compress enough fuel to ignite.

Ph.D. “If you can eventually create a spark plug and compress the fuel, direct drive has many properties that lend themselves to fusion power compared to indirect drive,” says Varchas Gopalaswamy ’21. (mechanical engineering), an LLE scientist who led a second study investigating the effects of using a direct excitation approach on megajoule-class lasers similar in size to NIF. “Following the scaling of OMEGA results to several megajoules of laser energy, it is predicted that fusion reactions will become self-sustaining, so-called ‘burning plasmas.’

Gopalaswamy says direct-drive ICF is a promising approach to achieving fusion ignition and clean energy in laser fusion.

Technological innovation and collaboration

“A key factor in the success of these latest experiments is the development of a new explosion method based on statistical predictions and validated by machine learning algorithms,” said Riccardo Betti, LLE Chief Scientist and Robert L. McCrory Chair Professor. in mechanical engineering and physics and astronomy. “These predictive models allow us to narrow down the pool of promising project candidates before conducting valuable experiments.”