The design of a power plant based on Inertial Confinement Fusion (ICF) must not only ensure the systems are robust enough to withstand the rigors of repeated high-energy pulses but, critically, also achieve sufficient gain.
A new study from University of Oxford spin-out First Light Fusion presents a path to the high gain fusion technology which it says would drastically reduce the cost of fusion energy. This model is known as Fusion via Low-power Assembly and Rapid Excitation (FLARE).
This paper notes that ICF requires enormous amounts of energy to compress and ignite the fusion fuel, yet typically less than 1% of that energy actually couples to the target. The extent to which a fusion reaction produces more energy than is delivered to the fuel, known as gain, is therefore key. The current record gain for ICF, achieved in May 2025 at the US Department of Energy’s National Ignition Facility (NIF), is just four but according to First Light economic modelling, a gain of at least 200 is needed for fusion to be commercially competitive, while a gain of 1,000 could deliver power at exceptionally low cost.
The FLARE concept is designed to achieve these gains of up to 1,000 through a step change in the design approach. The crux of this approach is simplifying the driver, which are conventionally extremely powerful and require near-perfect precision. These requirements drive costs into the billions and stretch development timelines far beyond practicality. The FLARE approach shifts more of the performance burden onto the target while also designing a reactor that is inherently robust, scalable, and affordable.
Cutting driver energies
The conventional ICF approach both compresses and heats the fuel at the same time to achieve ignition. This configuration requires precise symmetry, pulse shaping, and timing as the simultaneous heating opposes compression, increasing driver energy and power specifications. One method of reducing driver energy requirements is to decouple the compression and heating stages. This is the FLARE approach: first compressing the fuel in a controlled and highly efficient manner to high densities without forming a central hotspot and then using a separate process to ignite the compressed fuel by rapidly heated a small area using a short, intense pulse, typically delivered by a laser or charged particle beam. Carefully tailored compression of the fuel minimises its heating (and consequently pressure), making it easier to assemble to the high densities required for ignition. This approach – known as fast ignition –eliminates the need for ultra-precise implosion symmetry as no highly converged hotspot needs to be formed. It also removes the energy budget required to form a hotspot in pressure equilibrium with the surrounding fuel.
First Light argues that the separation of the heating and compression allows compressive work of the fuel to be maximised with (ideally) no increase in entropy. It emphasises this point, noting that minimising entropy represents a key efficiency of a particular fusion scheme and observing that the efficiency benefits of isentropic fuel compression have been recognised from the very beginnings of ICF research.
A second element of the strategy to reduce the energy and power needed for ignition is to minimise energy losses from the system. This energy can escape via several channels, First Lights says, including thermal conduction, hydrodynamic expansion, and critically in the fusion conditions under consideration, radiative losses. As the fuel heats up, it emits radiation, which can escape and carry away energy unless trapped. In principle, it is possible to accomplish this by achieving extremely high fuel densities, such that the fuel is opaque to its own thermal X-ray emission. However, this requires an accordingly large compression provided by a faster implosion and greater driver power delivered to the target. Operating at lower power, and therefore lower assembled fuel densities, necessitates an alternative mechanism for reducing these radiative losses. This challenge can be addressed by encasing the fuel in a high-opacity (typically metallic) pusher that implodes and compresses the fuel. The radiation field from the hot fuel establishes thermal equilibrium with the compressed pusher, recycling a portion of the emitted radiation back into the fuel. Suppressing radiative losses in this way significantly lowers the ignition temperature from approximately 5-10 keV (1 keV = 11.6 million K) in traditional hotspot ICF to as low as 2.5 keV. This configuration, known as “equilibrium ignition” is well established and recognised as part of a minimum energy route to fusion ignition. Another significant difference to the conventional hotspot scheme arising from this change is that the fuel is typically heated in a uniform way throughout its full mass. Volumetric burn is typical of equilibrium ignition, but it fundamentally limits the achievable target gain, since the entire fuel volume must be heated homogeneously. While values close to the minimum viable gain required for commercial ICF are theoretically possible, real-world effects will prevent its realisation. Higher gain volumetric target designs are therefore desirable to ease the margin on other reactor components, says First Light.
Once ignition occurs, maximising fusion yield from the compressed fuel is critical. The total fusion yield is limited by expansion and cooling after ignition. Expansion occurs in response to the rapid increase in internal pressure after ignition and can quench the burn prematurely, that is, before a substantial amount of the fuel is burned. A high-density pusher can tamp this expansion, keeping the fuel compressed for longer, for an increased burn fraction. As a result, the required fuel mass is also reduced, which in turn reduces stress factors on the chamber and wider reactor infrastructure. However, the high pusher mass, typically more than an order of magnitude greater than the fuel mass, can restrict gain potential unless further accounted for in target design.
Towards economically viable fusion
First Light notes that delivering inertial fusion as a viable power source requires a structured and transparent research pathway that enables stepwise progress, grounded in fundamental science and supported by the broader research community.
Within this framework, the economic viability of a viable ICF concept is dominated by the design of the target. The target is not merely a consumable, notes First Light. It argues that the target dictates the specification of the fusion driver, repetition rate, chamber architecture, and supporting balance-of-plant systems. Variations in achievable yield per shot directly influence the frequency of operation required to meet plant-level power output thereby impacting capital expenditure, operational costs, and overall system efficiency. Consequently, the selection of the target concept is pivotal as it defines the trajectory and cost profile of the research and development (R&D) pathway.
Target choice also determines not only the technical but also the financial contours of development; investment principles become central. A core principle of infrastructure investment is that risk and capital deployment must be aligned. Early-stage technical risk elevates the financial discount rate, limiting investability and slowing progress. Therefore, the two key investment questions for any fusion concept are:
- Risk-adjusted cost minimisation: Does the approach lower the integrated, risk-weighted cost of delivering grid-connected fusion power?
- Value maximisation: Does the resulting power plant, and the innovations generated along the development pathway, deliver long-term commercial returns?
Given the early stage of development, providing precise cost projections would imply a false level of certainty, says First Light. Instead, it emphasises the underlying physical and engineering principles. Key to commercial fusion is a development pathway that leverages established research, argues First Light. Its concept builds upon decades of inertial confinement research, consolidating proven scientific insights with proprietary technologies developed in-house. By adopting a component-first methodology, the system also can be decomposed into modular subsystems that are amenable to rapid, low-cost testing on existing facilities. This approach mitigates risk by isolating potential failure modes early, reducing overall program exposure.
High confidence in system performance can be achieved through rigorous modelling and sub-scale validation rather than full scale testing. Applying this philosophy reduces technical risk and enables progress without waiting for large demonstration facilities. This approach also invites collaboration with academic institutions and the wider fusion community, ensuring transparency and reproducibility while reducing risk. Through partnerships and shared research programmes, a broad peer reviewed base of evidence can be assembled to validate the performance and scalability of each subsystem.
A route to commercialisation
Given the target is the dominant lever for system performance its design governs achievable gain and, consequently, plant economics. The ability to prototype and evaluate targets at high cadence, combined with advanced simulation and data science tools, is central to enabling accelerated feedback loops.
First Light believes that the initial phases of development can be executed on current experimental platforms, minimising capital outlay while reducing risk. The company’s experimental platforms provide capabilities for target compression and shock generation but it also works in partnerships such as the CRADA project with Sandia National Laboratories, the Z Fundamental Science Program and the Prosperity Partnership. In addition, engagement with external laser laboratories enables investigation of ignition physics without the immediate need for new high-cost infrastructure. This approach, says First Light, has already demonstrated results. For example, its Big Friendly Gun (BFG) apparatus achieved pressures of 2.5 TPa in quartz, illustrating that capabilities once requiring multi-billion-dollar national facilities can now be reached with lower-cost, modular systems.
The transition from component validation to net energy gain will ultimately require a dedicated pulsed power driver. Scaling laws indicate that a gain-relevant pulsed power machine could be constructed for $100m–200m, representing less than 5% of the inflation-adjusted cost of the upgraded National Ignition Facility. Critical to success in this approach are:
- Mature Driver technology (high TRL): Reduces technical and supply chain risks.
- Lower Intensity: Enables cost-effective, robust systems with reduced component stress.
- Integration Flexibility: Compatibility with existing short-pulse laser facilities for hybrid component validation.
- Staged Investment: Capital commitments can be deferred until major technical risks are retired, improving risk-adjusted returns.
Other power plant challenges can be addressed more effectively through rapid derisking and the shared risk–reward dynamics of a strong partnering ecosystem. By simplifying the most difficult technical hurdles, opportunities open for technology transfer and read across from adjacent industries, accelerating progress and reducing development costs. In addition, partners stand to benefit from the broader innovation journey itself. Further value is likely to emerge along the path toward commercial fusion energy and these intermediate innovations not only enhance the return on investment for partners but also build momentum and confidence in the long-term goal of delivering fusion power.
Achieving successful fusion power
High gain is the single most important determinant of fusion power plant economics and First Light argues that its FLARE model can in principle achieve significantly higher gains for the same driver energy or the same gain for lower energy. The approach offers a significant potential reduction in ignition threshold energy compared to conventional hotspot inertial confinement fusion. It proposing a new pathway focused on simplicity, efficiency, and real-world power plant economics the concept rests on three key pillars:
- Innovative target design: Rather than relying on ultra-precise, high-power lasers, First Light uses cylindrical targets with a dense, opaque pusher to compress the fuel using modest input energy. Losses are reduced, confinement is improved, and ignition is triggered by an auxiliary source such as a short-pulse laser or pulsed power system. By decoupling compression and heating, this approach lowers the power required from the driver whilst enabling higher energy gain.
- Pulsed power-driven fuel compression: Pulsed power offers a lower-cost, higher-efficiency alternative to lasers and the First Light low-voltage design eliminates complexity that has historically limited pulsed power-driven ICF.
- A lithium pool reactor: In the First Light design, fusion reactions take place inside a liquid lithium pool dynamically structured with inert gas. This design absorbs neutrons, breeds tritium, captures heat, and protects the reactor walls without complex solid structures. It, says First Light, extends reactor lifetime, lowers costs, and positions the technology as a source of tritium, vital for both inertial and magnetic fusion.
First Light argues this approach creates an integrated system in which the driver, target, and reactor are mutually compatible, robust, and economically attractive.
