Xcimer Hires University of Rochester Fusion Scientist Cliff Thomas

Xcimer Energy Hires University of Rochester Fusion Scientist Cliff Thomas

DENVER, Colo. - September 23, 2026 - Xcimer Energy today announced that Cliff Thomas, a leading researcher in inertial confinement fusion from the University of Rochester's Laboratory for Laser Energetics (LLE), has joined as the new Chief Scientist for Xcimer's fusion program.

Thomas brings extensive expertise in inertial fusion, numerical modeling and target design to Xcimer as the company advances its laser-fusion architecture from experimental validation toward commercial power generation.

"Cliff has been part of the community working on the science behind Xcimer's approach for years, so we've seen his skills firsthand," said Conner Galloway, co-founder and CEO of Xcimer Energy. "Bringing him into the in-house team is an important step as we build the scientific and engineering capabilities required to turn laser fusion into a power plant."

Thomas joins Xcimer after working at the University of Rochester's Laboratory for Laser Energetics, one of the world's leading centers for high-energy-density physics and inertial confinement fusion research. His research has focused on implosion physics, indirect and direct drive, and requirements for ignition and high gain.

Thomas' LLE research has focused on the physics direct drive, and the potential benefits of scale and energy and requirements for ignition and high gain.

Before the LLE, Thomas spent more than a decade at Lawrence Livermore National Laboratory, where he proposed and demonstrated the first low gas fill HDC implosions on the NIF, which quickly met and exceeded all prior results, and set the stage for successes to follow.

Thomas has also worked with Xcimer for several years. He was part of the broader Xcimer research team participating in the company's experimental program at Rochester's OMEGA Laser Facility, including simulations and experiments supporting Xcimer's two-beam approach to inertial fusion energy.

"Xcimer is tackling a uniquely important problem: how to take the demonstrated physics of laser fusion and engineer it into an economically viable power system," said Cliff Thomas. "The company's approach brings together a different laser architecture, target design and power-plant architecture with a clear focus on commercial scalability. I'm excited to join the team at this stage and help turn that vision into reality."

Thomas has doctorate and master's degrees in mechanical engineering from Stanford University, and an undergraduate degree in mechanical engineering from Rice University.

A Crucial Time for Xcimer

Thomas's appointment further strengthens Xcimer's team of scientists and engineers drawn from leading national laboratories, universities and industry as the company works to build a commercially viable laser-fusion power system.

"Commercial fusion will require bringing together extraordinary capabilities in laser physics, plasma physics, target design, materials, pulsed power and power-plant engineering," said Alexander Valys, co-founder and president of Xcimer Energy. "Cliff adds exactly the kind of deep scientific expertise we need as we move into the next phase."

Thomas's appointment comes as Xcimer advances its commercial fusion roadmap. In June, the company launched operations of Phoenix, the world's largest privately owned laser system, which demonstrates key elements of Xcimer's excimer-laser and gas-optics architecture.

This summer, the US Department of Energy approved the preconceptual design and technology roadmap of Xcimer's commercial power-plant architecture, Athena, as part of the DOE's Milestone-Based Fusion Development Program. The milestone positions Xcimer among the front runners to commercialize fusion energy and marks one of the industry's most comprehensive government reviews of a privately developed fusion plant architecture.

Earlier this month, Xcimer and RTX announced a partnership to develop scalable multi-kilojoule-class pulsed-laser technologies. The companies plan to demonstrate the integration and containerization of Xcimer's pulsed-laser technologies into RTX's air defense systems, offering the U.S. military new directed energy capabilities to defeat airborne threats at lower costs.

RTX also announced it invested in Xcimer, directly strengthening Xcimer's laser fusion energy roadmap. The core challenge in both laser fusion and laser defense is identical: build a pulsed excimer laser that fires pulses repeatedly and reliably at a low cost per joule and is also mass-manufacturable; while demonstrating laser maintenance, efficiency and operational performance.

Read this letter from Xcimer's founders about how this move advances both fusion energy and defense.

About Xcimer Energy

Xcimer is building the biggest, brightest, and most powerful lasers to enable commercial fusion energy and transform air defense. Denver-based Xcimer expects to deliver fusion energy to the grid by the mid-2030s. Xcimer has raised nearly $200M from top-tier energy and technology investors, including Breakthrough Energy Ventures, Lowercarbon Capital, Emerson Collective, Prelude Ventures and many others. Xcimer received the largest laser fusion award from the U.S. Department of Energy's Milestone-Based Fusion Development Program. Visit xcimer.energy.

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