Three fusion companies in DOE’s Milestone program have updates

Three U.S. companies participating in the Department of Energy's public-private Milestone-Based Fusion Development Program recently have reported new developments. Xcimer Energy, Zap Energy, and Commonwealth Fusion Systems are among the eight companies that the DOE selected in 2023 to develop fusion pilot plant designs and resolve related scientific and technological challenges within 5-10 years.

The goal of the Milestone Program is to accelerate privately funded fusion companies toward commercial viability with the assistance of targeted public-private investment that is linked to independently verified technical and commercial "milestones."

Xcimer Energy: One of two companies in the DOE Milestone Program working on an inertial confinement concept, Xcimer announced that it has finalized an agreement to receive as much as $30.5 million in additional Milestone Program funding after it successfully completes and receives independent verification of certain preagreed technical and commercialization achievements.

Those achievements are linked to the company's development of an excimer laser system for a commercial fusion power plant. Instead of using large numbers of solid-state laser beams and costly optical components, as in conventional approaches to inertial fusion, Xcimer's system is based on "cost-effective gas lasers, durable gas optics, and a two-beamline configuration designed to deliver megajoule-scale laser energy repeatedly and economically," according to the company.

Xcimer cofounder and CEO Conner Galloway said of the new funding agreement, "We have moved from proving that the physics works to building the industrial technology that can turn fusion into a commercial energy source. This additional milestone funding gives us another powerful mechanism to accelerate that work while keeping the majority of the investment and risk in the private sector."

The company hopes to have its excimer laser-based fusion system ready to deliver electricity to the grid by the mid-2030s. It previously announced several developments this year as it advances its laser fusion architecture and expands its high-energy laser development programs toward that goal.

In June, for example, Xcimer launched the operation of its Phoenix prototype system, which it described as "the world's largest privately owned laser system, which demonstrates key elements of Xcimer's excimer-laser and gas-optics architecture." Also in June, the DOE approved the preconceptual design and technology road map milestones for the company's commercial power plant architecture, Athena.

Zap Energy: One of two companies in the DOE Milestone Program developing "innovative" power plant concepts that do not fit into established fusion confinement categories, Zap announced DOE approval of two capacitor development milestones: a pulsed power capacitor designed for the repetition rate and operating lifetime of a fusion power plant and a first prototype capacitor designed, manufactured, and tested entirely at the company. According to Zap, achievement of these two milestones demonstrates "progress in both long-life capacitor design and the U.S.-based manufacturing capabilities needed to produce these components at scale."

The company has been developing a type of pulsed-power fusion technology that it calls sheared-flow-stabilized Z-pinch, which it says "uses pulses of electrical current to compress a plasma column approximately 50 centimeters long. As the plasma compresses, carefully controlled axial flow stabilizes the pinch, enabling the temperatures and pressures required for fusion."

The newly approved pulsed-power capacitor design consists of a 35-kV, actively-cooled capacitor that is rated for 50,000 amps of peak current and is projected to continue functioning for 6 billion pulses. According to Zap, the capacitor "uses self-healing metallized polypropylene film, which degrades gradually rather than failing outright, and places several capacitor sections in series inside each winding so the film sees only a small fraction of the terminal voltage."

The DOE-approved prototype is a compact, 2.8-pound epoxy-potted capacitor designed with the same multisection winding approach used for the other approved capacitor. Developed, assembled, and tested in-house, it was cycled hundreds of times at 8 kV and at more than 7,000 amps, and its capacitance held steady to within 0.25 percent across the full test campaign.

Zap CEO Zabrina Johal noted that "commercial fusion requires more than achieving fusion conditions. It requires the technologies around the fusion core to operate reliably, repeatedly, and at power plant scale. Pulsed power is one of those critical enabling technologies. These milestones demonstrate progress toward the long-life, high-repetition-rate systems a commercial fusion plant will need while building the manufacturing capability to produce them here in the United States."

Commonwealth Fusion Systems: CFS is one of the companies participating in the DOE Milestone Program as a magnetic confinement tokamak fusion developer. It reports that the DOE has selected it as the only private company to lead a project in the government's Genesis Mission, which is using partnerships between national laboratories, industry, and academia to apply artificial intelligence to energy generation, scientific research, and national security.

The CFS-led project is focused on the development of an AI-enabled digital twin platform to optimize the operations of the company's SPARC prototype fusion machine, which is currently being assembled in Devens, Mass. The company expects SPARC "to achieve the first commercially relevant demonstration of net fusion energy and . . . pave the way for CFS to build and optimize ARC [SPARC's planned successor] commercial fusion power plants," it said.

The project will involve the use of DOE supercomputers to process fusion data, strengthen AI tools, and advance digital twin visualization work that was previously started by CFS, Nvidia Corporation, and Siemens. CFS said the project will include "building the software infrastructure to connect to DOE computing resources; building the training datasets and AI surrogate models needed for an AI-enabled digital twin; training reinforcement learning and agentic AI models to be used by an AI-based SPARC operations co-pilot; and building data visualization pipelines that accelerate operations."

CFS expects the AI-enabled digital twin to help accelerate commercial fusion deployment "by allowing rapid iteration in the SPARC control room."

CFS cofounder and chief science officer Brandon Sorbom said that the project "will convert decades of R&D performed across the U.S. fusion community into tools that can be applied to accelerate SPARC operations. Together, our team of public and private leaders in AI and fusion will be able to unify and apply decades of U.S. research and tackle some of the fusion industry's biggest challenges."