The DEMO Low Aspect Ratio (LAR) Review, held from 17–20 November 2025, brought together scientists and engineers to assess progress on Europe’s fusion power plant concept (DEMO). The review marked a milestone since the first Gate Review in 2020, providing a comprehensive assessment of physics, critical systems, technology R&D, and design integration, while offering recommendations to support the roadmap toward a future fusion pilot plant.
The formal evaluation was conducted by a small panel of experts, while the other participants— 100 in total—actively joined the discussions, listened to presentations, and contributed to the broader exchange of ideas. The three key objectives for this review focused on 1) presenting an overview and status of the critical systems, technology R&D, and design activities for DEMO LAR 2) addressing lessons learnt and their relevance for future investments and potential Public–Private Partnerships, with a particular emphasis on knowledge management and 3) providing input to the explorative study in support of the future fusion pilot plant and the wider EU fusion roadmap.
Through these objectives, the review provided strategic guidance on current progress while highlighting priorities for the next phase of Europe’s fusion development effort.
Over four days of structured technical sessions, the review panel evaluated advances across DEMO’s physics basis, systems integration, tritium fuel cycle, power exhaust, magnet technologies, breeding blanket design or safety considerations.
The agenda comprised ten major thematic blocks, spanning system codes, physics coupling, vacuum vessel design, and fuel breeding systems. The sessions highlighted the status of the DEMO LAR design and its alignment with Europe’s strategic objectives for fusion-based energy production.
A key observation throughout the review was the increasing coordination between teams and the need for closer integration of physics, system code development, engineering designs, and supporting technologies. This growing synergy reflects DEMO’s transition from pre-conceptual analyses toward more advanced design stages.
Benoit Salamon from CEA, Chair of the Review Panel highlighted the significance of the event:
“This review was the opportunity for EUROFUSION to receive external feedback on the orientations and methodologies they have been applying in order to solve some of the most challenging engineering/physics issues on the path of a feasible fusion based reactor. The discussions were highly fruitful, mobilized a lot of return of experience from the panel experts, and will likely contribute to more improvements and efficiency when pushing their research further.”
Lorenzo Giannini, Design Integration Lead from the DEMO Central Team, emphasized the importance of early simplifications and coordinated design work:
“The DEMO gate review shows how solid preconceptual analyses and targeted simplifications can keep technical complexity well under control, even for devices larger than ITER. Looking ahead, I believe that close coordination between teams working on specific systems and integrators will be crucial to guiding the design toward coherent, feasible, and well-justified engineering solutions for a Fusion Pilot Plant.”
Francesco Maviglia, Plasma Systems Division Head, DEMO Central Team underlined the role of integrated physics and engineering in shaping the future device:
“The in-house DEMO Central Team and the Work Packages expertise strengthened the design approach by integrating physics and engineering consistently from the very beginning, allowing system codes to converge toward more coherent design points and embedding uncertainties and margins explicitly. High fidelity codes and the full discharge flight simulator validate the design and transient phases and feed back into the workflow models in a high-to-lower fidelity cycle, allowing the workflows to be used with greater confidence to support future design explorations adapted to different fusion plant requirements. This resulted in the proposed DEMO Low Aspect Ratio configuration, which is more robust and satisfies the stakeholder requirements, while a continuously updated improvement list highlights potential innovation R&D areas.”
The Road Ahead
The review will be concluded with a report providing recommendations for the next steps stages of fusion research including engagement with potential private-sector partners. DEMO’s increasing design maturity, strengthened by extensive European collaboration, positions the program on track to deliver fusion electricity as a safe, sustainable, and scalable energy source in the coming decades.