Marvel Fusion’s path to economically viable laser-based inertial fusion energy

Marvel Fusion is developing economically viable laser-based inertial fusion energy through advancements in laser technology, fuels, and fast-ignition concepts, aiming to deliver reliable, clean energy without long-lived radioactive waste.

Founded in 2019, Marvel Fusion is an innovative fusion company in the field of laser-based inertial fusion energy. The company focuses on advances in laser technology, fuels, and fast-ignition concepts that can be integrated into validated target concepts while also opening pathways toward highly advanced fusion target designs. To pursue these goals, Marvel Fusion combines innovations in nanotechnology, ultra-fast lasers, and advanced fuels.

Fusion

Fusion power plants have the potential to deliver reliable baseload electricity to support rising global energy demand while avoiding the emission of climate-relevant gases. By comparison, fluctuating renewable sources are intermittent and, without large-scale energy storage (multi-TWh capacity), can only contribute a limited share if overall grid stability is to be preserved. In contrast to nuclear fission, nuclear fusion does not produce long-lived radioactive waste, and its fuels are abundant and broadly accessible.

Marvel Fusion

Marvel Fusion (MF) is a fusion company investigating commercially viable routes to laser-based Inertial Fusion Energy (IFE). One of its central activities is the development of advanced fast-ignition concepts leading to novel target designs, but that may also be integrated into existing ones.^1-3 Another key focus is the development of advanced ultra-broadband, diode-pumped solid-state lasers (DPSSLs) and beyond, which can operate in both ultra-short and long-pulse regimes at high repetition rate, high pulse energy, high efficiency and low cost, enabling their use as versatile IFE drivers across a wide range of applications. Marvel Fusion is also pioneering work on advanced cryogenic fuels with controlled contaminants as well as non-cryogenic fuel systems that offer potential advantages for commercial fusion energy. In the following sections, the company’s activities are described in more detail.

The role of fast ignition

An important parameter in the context of laser-based IFE is the so-called target gain QT, defined as the ratio of fusion energy to the laser energy deposited in the target. Sufficient target gains for power plant applications are in the range of QT ≈ 30 − 100, depending on the overall efficiency of the power plant. The target gain depends on some form of primary laser energy conversion into useful secondary energy, followed by hydrodynamic processes and fusion-energy production. Hence, the target gain can be expressed with the help of a product of three efficiency parameters as QT = η_x η_h η_b, where the parameter η_x may, for example, denote the fraction of laser energy converted into secondary energy carriers that heat parts of the fuel capsule, ηh the hydrodynamic efficiency comprising all hydrodynamic processes required to compress the fuel capsule and to create a hotspot, and η_b the fusion amplification by a burn wave. For the hohlraum target concept at the NIF, one typically has ηx ≈ 0.1 for the fraction of laser energy converted into x-rays that heat the ablator of the fusion capsule, η_h ≈ 0.1 for the hydrodynamic efficiency of the fuel compression and hotspot formation processes driven by the heated ablator due to the absorbed x-rays from the conversion step before, and ηb ≈ 400 for the burn-wave efficiency producing the fusion energy. The triple product of efficiencies in¹ should be as large as is possible for high target gain.

In the literature, essentially two ways to ignite fuel are discussed, implying substantially different efficiency triple products. One is volume ignition, and the other is hotspot ignition. Under ideal assumptions, volume ignition of deuterium-tritium (DT) fuel typically requires that a quantity called the density–range product ρDTR of DT satisfies ρDTR > 0.5 and that the DT temperature simultaneously exceeds kT_e > 6 keV.⁴ Under realistic conditions, volume ignition is even more demanding. Hotspot ignition requires the generation of a hotspot embedded into cold fuel capable of driving a burn wave. Hotspot ignition is possible if the triple product ρ^hDT R^h kT^h_e⁵ exceeds the threshold given by

(2)

where ρ^hDT is the mass density of the fuel inside the hotspot, ρ^cDT is the mass density of the surrounding cold fuel, R^h is the hotspot radius, and kT^h_e is the hotspot temperature. The constant is C ≈ 6 for DT and C ≈ 60 − 150 for non-cryogenic DTs⁴ over the relevant parameter range. The densities are given in g/ccm, the radius in cm, and the temperature in keV. The advantage of hotspot ignition is that it principally enables the control of the relevant parameters of the triple product and the threshold parameters in² implying enhanced target gains.

Traditional fast-ignition strategies seek to raise the temperature kThe in high-density fuel. However, heating fuel at high density with high efficiency is intrinsically difficult. A more effective strategy is to heat fuel at low density efficiently while compressing the surrounding cold fuel more moderately. This approach requires advanced laser–matter coupling physics and ultra-fast laser technology, because the heating of the hotspot must be fast and synchronised with the compression of the cold fuel. MF suggests that ultra-fast hotspot ignition is possible using the highly efficient coupling physics between ultra-short laser pulses and nano-structured materials, as they are explored by the company.

The role of advanced fuels

At present, DT ice is used as the predominant fusion fuel since it has the least requirements for ignition. However, in a commercial setting, contaminated cryogenic DT and low-Z compounds that contain DT (see Table 1) might be more suitable. Some of them are solid, i.e. non-cryogenic at room temperature. Interestingly, under ideal conditions these fuels can be volume ignited for ρDTR ≥ 0.35 g cm⁻² and kT_e ≥ 15 keV as Fig. 1 shows, i.e., parameters which are demanding but still on the same order of magnitude as those for DT ice under the same ideal assumptions, since for temperatures greater than 10 keV their ability to absorb in situ fusion energy is enhanced compared to DT as Fig. 2 shows.

The role of nanorods

One core element of the fast igniter are nanorods. A selection of fabricated high-quality nanowires with appropriate parameters is shown in Fig. 3. By tuning their lengths, thicknesses, and pitches to match the wavelength, intensity, and energy of the impinging ultra-short laser pulses which power them, they can be optimized for maximum laser energy absorption and conversion into new useful energy carriers. MF has succeeded in fabricating high-quality nanowires across a broad parameter range, enabling compatibility with a wide spectrum of laser conditions and conversion requirements. Experiments show that these nanowires can convert nearly the entire incident laser energy into secondary energy carriers suitable for efficient fuel heating on sub-ps timescales. The nanowire-based fast-igniter concept can scale to multi-MJ hotspots, supporting very high fuel temperatures kT^h_e across flexible hotspot radii R^h, thereby surpassing the threshold for the triple product ρ^hDT R^h kT^h_e⁵ required by the hotspot condition.² The versatility of this approach for high target gain is high.

The role of advanced lasers

Another core element of the fast igniter is the driver laser. Modern fusion driver lasers are modular, implying they consist of multiple subsystems, some operating in the long-pulse and others in the ultra-short-pulse regime. The fast igniter requires ultra-high-contrast, ultrashort laser pulses with sufficiently high pulse powers and energies. While such lasers were out of reach only a few years ago, they are now becoming technologically feasible, as shown in Fig. 4. Likewise, the compression lasers must reach adequate power and energy levels defined by the parameters needed for efficient hotspot ignition.

Strategy of the company

The limited access of commercial fusion companies to advanced laser facilities makes it difficult to experimentally validate fundamentally new target concepts. Hence, MF utilises improvements to established target designs as a meaningful and practical step forward to commercialise fusion energy. In addition, novel target concepts are developed by the company.

MF investigates a novel fast ignition concept which is capable of igniting a range of fuels comprising wetted foams, contaminated DT, and a range of advanced noncryogenic fuels. The igniter concept of the company requires the availability of advanced, highly efficient ultrabroadband laser technology. The frequency converted Nd:glass-based DPSSLs of the company with wall plug efficiencies around 10% can serve as an initial platform, but future systems must be substantially more capable, allowing for significantly enhanced performance at lower cost.

In addition to its fast ignition technology, MF considers advancing efficient diode-pumped ultrabroadband lasers scalable in energy and average – as well as peak-power of utmost importance for paving the way to commercially viable laser-based IFE.

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References

1. H. Abu-Shawareb and et al. (Indirect Drive ICF Collaboration),“Lawson criterion for ignition exceeded in an inertial fusion experiment,” Phys. Rev. Lett. 129, 075001 (2022).
2. A. L. Kritcher and et al., “Design of an inertial fusion experiment exceeding the lawson criterion for ignition,” Phys. Rev. E 106, 025201 (2022).
3. V. Gopalaswamy, C. Williams, R. Betti, and et al., “Demonstration of a hydrodynamically equivalent burning plasma in direct-drive inertial confinement fusion,” Nature Physics 20, 751–757 (2024).
4. H. Ruhl, C. Bild, O. Pego Jaura, M. Lienert, M. Nöth, R. Ramis Abril, and G. Korn, “Properties of noncryogenic DTs and their relevance for fusion,” Journal of Applied Physics 137 (2025).
5. S. Atzeni and J. Meyer-ter Vehn, The physics of inertial fusion: beam plasma interaction, hydrodynamics, hot dense matter, Vol. 125 (OUP Oxford and citations therein, 2004).

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