• Athena is the architecture for Xcimer's fleet of fusion power plants, designed for continuous operation and integrating the company's proprietary excimer laser platform with target delivery, fusion chamber, tritium breeding, and power generation systems engineered from the outset for industrial scale.
• Milestone positions Xcimer among the leading companies racing to commercialize fusion energy at industrial scale.
• News comes a week after Xcimer began operating Phoenix, the largest privately owned laser system in the world and the company’s prototype for commercializing laser fusion.

Xcimer Energy today announced that the U.S. Department of Energy (DOE) has formally approved the company's preconceptual design and technology development roadmap milestone for Athena, Xcimer's architecture for fusion power plants.

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Athena, Xcimer's reference architecture for commercial laser fusion power plants, is designed for continuous operation, industrial scale, and a fuel cycle that renews itself. Credit: All images (c) 2025 Kilograph

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. The acceptance of both the design and roadmap also reflects continued progress under the DOE's Fusion Milestone Development Program and validates Xcimer's roadmap for translating laboratory fusion breakthroughs into a commercially deployable energy system.

Athena is the reference architecture for Xcimer's fleet of fusion power plants. Designed for continuous operation, Athena integrates the company's proprietary excimer laser platform with target delivery, fusion chamber, tritium breeding, and power generation systems engineered from the outset for industrial scale.

Xcimer’s 724-page submission provided DOE reviewers with a detailed assessment of plant performance targets, economics, system-level engineering requirements, safety and environmental analyses, and technology development pathways required to achieve commercial fusion power.

"The question facing laser fusion is no longer whether the physics works," said Conner Galloway, CEO, Chief Science Officer, and co-founder of Xcimer Energy. "The question is how fast we can industrialize it. DOE's acceptance of Athena reflects both the strength of our technical approach and our ability to execute against an ambitious commercialization roadmap."

The milestone comes a week after Xcimer announced the launch of operations of its prototype laser system, code-named Phoenix – the largest privately owned laser system in the world and the company’s prototype for commercializing laser fusion.

Phoenix, housed in Xcimer’s 74,000-square-foot Denver laser facility, is a proof of concept for an unconventional fusion architecture: a krypton fluoride (KrF) excimer laser using Stimulated Brillouin Scattering (SBS) to compress a microsecond-long pulse into the nanosecond timescales fusion requires. Phoenix is designed to demonstrate end-to-end integrated operation of excimer amplification and SBS pulse compression.

Athena: designed for the real world

Xcimer is designing for the real-world requirements of power plants, which are expected to operate continuously for decades. The company believes long-term economics, maintainability, fuel-cycle cost, and reliability will ultimately determine which fusion architectures succeed commercially.

“A commercially attractive power plant looks very different from a scientific breakthrough facility,” said Susana Reyes, Vice President for Chamber and Plant Design at Xcimer Energy. “We are designing Athena to run continuously at a repetition rate of up to 1 Hz, and the use of a liquid wall chamber maximizes availability by protecting the solid structures from the fusion reaction emissions over the entire plant lifetime."

The DOE’s acceptance of the Athena design follows Xcimer’s completion of earlier program milestones over the first 18-month budget period in the milestone program. The company’s next phases of work include full-scale subsystem testing, engineering validation, and preparation for an integrated plant demonstration.

"One reason other fusion chamber designs face a durability problem is that they put solid material where the fusion neutrons go. We don't. The molten salt curtain absorbs and moderates the flux, breeds fuel, and carries the heat — and it flows, so it renews itself continuously,” Reyes said. “We designed Athena around that property from day one, and it shapes everything: the materials choices, the thermal management, the maintenance philosophy, the economics. And Xcimer’s laser architecture uniquely enables this design."

The Milestone-Based Fusion Development Program is part of the DOE’s broader effort to accelerate the commercialization of fusion energy through public-private partnerships. Xcimer is among a select group of companies participating in the program, each pursuing different technical approaches to achieving commercially viable fusion power.

About Xcimer Energy Xcimer Energy is building on the only fusion approach that has exceeded scientific breakeven. The Denver-based company is developing an excimer-based laser fusion system designed to solve what the National Ignition Facility did not: the economics. Xcimer's architecture targets laser costs under $100 per joule and a chamber design requiring no first-wall replacement. Founded in 2022, Xcimer is backed by leading investors and selected for U.S. Department of Energy funding. Visit xcimer.energy.

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Department of Energy's approval on Xcimer's fusion power plant design and roadmap clear path for commercial laser fusion.