U.S. Naval Research Laboratory Advances Laser Technology for Fusion Energy Applications Through BETHE Program

WASHINGTON, D.C.   –   Scientists in the Plasma Division at the U.S. Naval Research Laboratory (NRL) are building on a multi-year research effort that demonstrated the potential of an advanced laser technology that could help enable future inertial fusion energy power plants.

Fundamental developments on repetitive pulsed power and other aspects of the research could allow breakthroughs in viability and support long-term Navy and national security objectives. The work was conducted as part of the Department of Energy’s Breakthroughs Enabling THermonuclear-fusion Energy (BETHE) program, a research initiative focused on developing a more efficient laser driver for fusion energy applications. 

NRL research explored the use of an argon fluoride (ArF) excimer laser as a next-generation driver for inertial fusion energy. Compared with conventional approaches, ArF lasers offer the promise of higher laser efficiency and increased target gain, two key factors needed to improve the viability of commercial fusion power.

“This program was about developing a new laser driver that could improve the overall efficiency of inertial fusion energy systems,” said Matthew Wolford, Ph.D., head of the Electron Beam Science and Applications Section at NRL. “Higher laser efficiency and higher target gain give fusion energy a better chance at eventual commercialization.”

Over the course of approximately three years, the NRL team evaluated the feasibility of scaling ArF laser technology for high-energy applications. One of the program’s key technical achievements was demonstrating laser outputs approaching 240 joules per shot, the largest argon fluoride laser performance reported to date, while identifying a pathway toward significantly higher wall-plug efficiency. This is the first demonstration of high energy capability for ArF lasers, although much higher energy will need to be achieved for applications such as fusion power plants.

“We were encouraged by both the laser output and the intrinsic efficiency measurements of argon fluoride,” Wolford said. “Those results suggest this technology could support fusion energy systems that require less input energy to reach ignition.”

The research also advanced critical enabling technologies, including electron-beam pumping techniques needed to drive the laser system. To reach higher pump rates, researchers increased current density in the laser’s cathode by roughly a factor of three, introducing new engineering challenges that the team addressed through design innovations and component testing.

Additional hurdles included developing large-scale optical components capable of operating at the laser’s 193-nanometer ultraviolet wavelength. Short wavelength allows the capability of coupling energy efficiently to fusion power plant targets as well as mitigating laser plasma instabilities, which hampers the laser energy to the target. This shorter wavelength improves the efficiency of the entire fusion power plant system from a high-level perspective.

NRL was uniquely positioned to conduct this work due to decades of experience in high-average-power laser research. From 1999 to 2009, NRL played a central role in the national High Average Power Laser program, where it developed the Electra krypton fluoride laser system and demonstrated long-duration, high-repetition-rate operation. NRL used some of the resources from the High Average Power Laser Program to demonstrate the initial technologies needed for an excimer laser driven fusion power plant.

“That prior work meant we already had the facilities and expertise needed to evaluate argon fluoride lasers quickly,” Wolford said. “There are very few places in the world with experience in electron-beam-pumped excimer lasers, and that’s a capability NRL has built over time.”

Beyond energy applications, the research has implications for future Navy and national security needs. High-power laser technologies and their underlying components may support a range of defense applications, particularly as emerging systems demand greater and more efficient power generation. Data centers for example will need a tremendous amount of power. More than can be produced presently.

“The power demands of using artificial intelligence and machine learning from data centers will force countries to adapt or be outpaced by those that do. We’re always looking for new ways to develop power generation technologies,” Wolford said. “As new capabilities come online that require large amounts of power, advances like this help expand the range of options available to the Navy and the warfighter.”

Although funding for the BETHE project has concluded, NRL researchers expect the work to inform future efforts in collaboration with the Department of Energy and private-sector fusion companies. The next step, Wolford noted, will likely involve transitioning the technology from laboratory-scale research to industry partners capable of building larger systems.

“Our role at NRL is to establish the scientific and technical foundation,” he said. “If industry chooses to pursue argon fluoride lasers for fusion energy, we’re well positioned to support that transition.”

The BETHE program involved a core team of approximately five to seven researchers and was conducted during the COVID-19 pandemic, requiring adaptability in the face of supply-chain disruptions and shifting experimental constraints, an experience Wolford says underscored the resilience of the research team.
“At NRL, you adapt and move forward,” he said. “That’s exactly what this team did.”

About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the U.S. Navy and Marine Corps from the seafloor to space and in the information domain. NRL, located in Washington, D.C. with major field sites in Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers and support personnel.

NRL offers several mechanisms for collaborating with the broader scientific community, within and outside of the Federal government. These include Cooperative Research and Development Agreements (CRADAs), LP-CRADAs, Educational Partnership Agreements, agreements under the authority of 10 USC 4892, licensing agreements, FAR contracts, and other applicable agreements.
 
For more information, contact NRL Corporate Communications at NRLPAO@us.navy.mil.