First Light Fusion publishes first plausible path to high gain, unlocking cheap fusion energy

• First Light Fusion presents first reactor-compatible path to "high gain" fusion, which would drastically reduce the cost of this limitless clean energy source.
• Gain (energy out divided by energy in – the efficiency of the fusion reaction) is *the* critical parameter in determining the cost of fusion energy
• Models show that FLF's new concept for high gain fusion – called FLARE – achieves an extraordinary gain of 1,000, compared to today's experimental level of 4, an order of magnitude higher than other proposed inertial fusion energy (IFE) schemes.
• FLF has published a white paper outlining its amplification technology and new, complementary power plant approach – with the paper having been endorsed by renowned physicists

OXFORD, England, Sept. 19, 2025 /PRNewswire/ -- First Light Fusion (FLF), Britain's leading IFE company, has published the first commercially viable, reactor-compatible pathway for high gain inertial fusion – a critical step toward delivering affordable fusion energy at scale, an ambition often hailed as energy's 'Holy Grail'.

In its new white paper, the University of Oxford spin-out outlines a novel, scientifically grounded approach to fusion energy called FLARE – Fusion via Low-power Assembly and Rapid Excitation. While the conventional IFE approach is to compress and heat the fuel at the same time to achieve ignition, FLARE splits this process into two: first compressing the fuel in a controlled, efficient manner and then using a separate process to ignite the compressed fuel, generating a massive surplus of energy, known as "fast ignition".  Though this has long been researched, First Light's unique amplification technology would now make it practical.

FLARE leverages First Light's 14 years of inertial fusion experience and unique controlled-amplification technology, creating a system capable of reaching the high gain levels needed for cost competitive energy production. This approach would underpin the design for commercial reactors that can be based on much lower power systems that already exist today, opening up an opportunity for partners to build those systems, using FLF's technology as the fuel, and roll it out worldwide.

Gain – when more energy is converted from the reaction than energy delivered to the fuel – has long been the missing link to full-scale commercial fusion. The record gain level is 4, achieved at the U.S. Department of Energy's National Ignition Facility (NIF). FLF's new FLARE concept could produce energy gain of up to 1,000. The company's economic modelling suggests that gain of at least 200 is needed for fusion energy to be commercially competitive, while gain of 1,000 would enable very low-cost power.

The FLARE model offers a cheaper development pathway and drives down the expected cost of a fusion power plant: an experimental gain scale facility is expected to cost 1/20^th that of NIF (the only facility that has achieved gain globally) and could be built using proven technologies. Due to the lower energy and power requirements of the FLARE technology, future commercial power plants would have significantly lower capital costs than other plausible IFE schemes, with lower complexity and core components such as the energy delivery system costing 1/10th of the capital cost of previous fast ignition schemes. The lower pulse rate (enabled by the high gain) also reduces operating costs. Since a pulsed system plant can adjust its output, it can provide flexible, low-cost electricity to support modern grids which utilise a high level of intermittent renewables.

By building on existing technology, FLF's approach accelerates inertial fusion deployment and has the potential to leverage existing supply chains, significantly reduce capital expenditure, speed up planning approvals and reduce regulatory hurdles in the deployment of commercial fusion plants.

FLF's new FLARE approach has received backing from prominent physicists, including Jeremy Chittenden, professor of plasma physics and co-director, Centre for Inertial Fusion Studies, Imperial College London.

Mark Thomas, First Light Fusion CEO, said: "This is a pivotal moment not just for First Light, but for the future of energy. With the FLARE approach, we've laid out the world's first commercially viable, reactor-compatible pathway to high gain inertial fusion – and it's grounded in real science, proven technologies, and practical engineering.

"Achieving a gain of 1000 puts us well beyond the threshold where fusion becomes economically transformative. Through our approach, we're opening the door to a new industrial sector — and we want to bring others with us."

Dr Robert Trezona, Partner, Cleantech at IP Group, said: "The FLARE concept and its development pathway are landmark endorsements of First Light's asset-light business model, paving the way, through partnership, to commercially viable nuclear fusion - a clean, near-infinite energy source. This breakthrough concept underscores the company's scientific prowess and focus on developing low-cost pathways to abundant clean energy, positioning it - and the UK - at the forefront of a trillion-dollar market. We first backed First Light in 2011 and are proud to have supported its journey. This new concept shows that the company can continue to do amazing things in fusion energy."

Lord David Willetts FRS, former Science minister and Chair of the Foundation for Science and Technology, said: "Fusion has often been dismissed as always 30 years away. That cliche fails to recognise how much real progress is being made, especially here in Britain.  First Light Fusion have now shown a credible pathway to viable commercial fusion. The challenge now is to ensure the UK leads the rapid development of this technology."

Links to the White Paper, Executive Summary and Notes to Editors.

SOURCE First Light Fusion