Private Fusion Ventures

Nuclear fusion energy development has long been led by government-driven large-scale projects, but private sector involvement has rapidly increased since the late 2010s. As of 2025, cumulative investment in fusion startups worldwide has exceeded $9.8 billion, and this field is growing as a new industry.

Background of Private Sector Entry

Challenges of Large-Scale International Projects

International cooperation centered on the International Thermonuclear Experimental Reactor (ITER) is progressing steadily, but it also faces challenges inherent to large-scale international projects. More than 40 years have passed since the concept was initiated in 1985, and first plasma ignition is scheduled for the mid-2030s. Construction costs have ballooned to several times the original estimate, and the complexity of decision-making due to coordination among seven countries and regions has also been noted.

In this context, private companies are pursuing different approaches to fusion commercialization. While government projects prioritize “certainty,” private companies tend to prioritize “speed.”

Technological Breakthroughs

The biggest factor driving private sector entry is the advancement of high-temperature superconducting (HTS) technology. Conventional low-temperature superconducting (LTS) magnets required cooling with liquid helium (4 K), but HTS materials such as REBCO (Rare Earth Barium Copper Oxide) can maintain superconductivity above liquid nitrogen temperatures (77 K).

In magnetic confinement fusion, the magnetic energy density $B^2/2\mu_0$ must be sufficiently large relative to the plasma pressure $p$. The beta value expressing this ratio is:

$$\beta = \frac{p}{B^2/2\mu_0} = \frac{2\mu_0 n k_B T}{B^2}$$

Since fusion power density is proportional to the product of temperature and plasma density:

$$P_\text{fusion} \propto n^2 \langle\sigma v\rangle \propto \frac{\beta^2 B^4}{T^2} \langle\sigma v\rangle$$

Higher magnetic fields dramatically increase fusion power density. With HTS magnets making fields above 20 T realistic, it has become possible to achieve equivalent performance while significantly reducing device volume.

Changes in Investment Environment

Since the 2015 Paris Agreement, investment appetite for decarbonization has rapidly increased. With the expansion of ESG investment and growing social interest in clean energy, venture capital funds have begun flowing into fusion, which had often been viewed as a “pipe dream.”

Since 2021 in particular, investment has accelerated due to several converging factors:

• Growing awareness of the urgency of climate action
• Need for baseload power to address the intermittency of solar and wind
• Dramatic improvements in plasma control technology through AI and machine learning
• Achievement of technical milestones by several startups

Structural Advantages of Private Companies

Private companies have the following structural advantages:

1. Rapid decision-making: Technical decisions can be made without bureaucratic processes
2. Flexible talent acquisition: Recruiting excellent talent through stock options and similar incentives
3. Technical risk-taking: A culture that tolerates failure and enables quick pivots
4. Clear milestones: Progress visibility through commitments to investors
5. Supply chain building: Early industrial infrastructure development with an eye toward commercialization

Major Venture Companies

Commonwealth Fusion Systems (CFS)

Company Overview

CFS, spun off from MIT’s Plasma Science and Fusion Center (PSFC), was founded in 2018. It takes an approach combining knowledge of high-field compact tokamaks cultivated at MIT’s Alcator C-Mod tokamak with the latest HTS technology.

In August 2025, the company completed an $863 million Series B2 round, bringing total funding to approximately$3 billion. This accounts for about one-third of all fusion startup funding, making it the most well-funded company. Major investors include Bill Gates, George Soros, Tiger Global, and Google.

Technical Approach

CFS’s core technology is HTS magnets using REBCO tape. In September 2021, the company successfully tested a toroidal field coil exceeding 20 T. This field strength is approximately four times ITER’s 5.3 T.

The advantage of higher fields can be understood from the relationship between energy confinement time $\tau_E$ and the fusion triple product. The confinement time of tokamaks is empirically expressed as:

$$\tau_E \propto I_p^{0.93} B_t^{0.15} n^{0.41} P^{-0.69} R^{1.97} \kappa^{0.78}$$

(IPB98(y,2) scaling law). Here $I_p$ is plasma current, $B_t$ is toroidal field, $n$ is density, $P$ is heating power, $R$ is major radius, and $\kappa$ is elongation.

Since plasma current can increase proportionally with the magnetic field while maintaining the safety factor $q$, higher fields improve confinement performance. Furthermore, if the allowable beta value is constant, higher fields enable higher density and higher pressure plasmas.

SPARC Project

CFS is building the demonstration reactor “SPARC” (Soonest/Smallest Private-funded Affordable Robust Compact) in Devens, Massachusetts. SPARC’s key parameters are:

• Major radius: 1.85 m
• Minor radius: 0.57 m
• Toroidal field: 12.2 T
• Plasma current: 8.7 MA
• Design $Q$: $Q \geq 2$ (target $Q \approx 10$)
• Fusion power: 50-140 MW

SPARC is the first private device aiming for “net energy gain”—producing fusion energy exceeding the input energy. First plasma is targeted for late 2025.

The fusion gain $Q$ is defined as:

$$Q = \frac{P_\text{fusion}}{P_\text{heat}}$$

$Q = 1$ is the break-even point, and at $Q > 1$ the output from fusion exceeds the heating input. SPARC has $Q \geq 2$ as its design criterion, with predictions that $Q \approx 10$ can be achieved under optimal conditions.

ARC and Commercialization Plans

Building on SPARC’s success, CFS is advancing the design of the commercial power plant “ARC” (Affordable Robust Compact). ARC will adopt the same high-field approach as SPARC but with a design premised on steady-state operation and connection to the power grid.

In 2025, CFS announced plans to build its first ARC power plant in Chesterfield County, Virginia. A 200 MW power purchase agreement has been signed with local utility Dominion. Operation is targeted for the early 2030s.

ARC design parameters:

• Electrical output: 200-500 MW
• Major radius: approximately 3.3 m
• Toroidal field: 9.2 T
• Fusion gain: $Q > 25$

TAE Technologies

Company Overview and History

TAE Technologies (formerly Tri Alpha Energy), founded in 1998, is one of the oldest fusion startups. Based on research by physicist Norman Rostoker at the University of California, Irvine, its ultimate goal is aneutronic fusion.

Total funding exceeds $1.2 billion, with an enterprise value of$6 billion. Major investors include Google, Chevron, Goldman Sachs, and Wellcome Trust.

Field-Reversed Configuration (FRC)

TAE employs the Field-Reversed Configuration (FRC) approach. FRC is a type of compact toroid—a plasma configuration with a self-organized magnetic field structure without external magnetic fields.

The FRC magnetic field structure is formed by the self-field created by plasma currents. Inside the separatrix, field lines are closed and independent from the open field lines outside. FRC equilibrium is described by the following pressure balance:

$$\nabla p = \mathbf{J} \times \mathbf{B}$$

A characteristic parameter of FRC is the “flux confinement ratio,” defined by the ratio of separatrix radius $r_s$ to external magnetic coil radius $r_c$:

$$\langle\beta\rangle = 1 - \left(\frac{r_s}{r_c}\right)^2$$

FRC can achieve extremely high beta values of $\langle\beta\rangle \approx 0.9$, which is overwhelmingly superior compared to typical tokamaks ($\beta \approx 0.05$). High beta means efficient plasma confinement.

Proton-Boron Reaction

TAE’s ultimate goal is fusion using the proton-boron (p-$^{11}$B) reaction:

$$p + {^{11}\text{B}} \rightarrow 3\,{^4\text{He}} + 8.68 \text{ MeV}$$

The greatest advantage of this reaction is that all products are alpha particles (helium nuclei), with no neutron generation. While the 14.1 MeV neutrons from D-T reactions cause activation and damage to structural materials, this problem is greatly reduced with the p-$^{11}$B reaction.

However, the cross-section of the p-$^{11}$B reaction is very small compared to the D-T reaction, and the optimal temperature is also higher (approximately 600 keV, more than 10 times that of D-T), requiring extremely high temperature plasmas. TAE is taking a staged approach toward this challenging goal.

Evolution of Devices

TAE has accumulated technology by progressively upgrading experimental devices:

• C-2 (2008-2012): Demonstration of FRC formation and beam-driven stabilization
• C-2U (2012-2016): Improved energy confinement with end plugs
• C-2W Norman (2017-present): 10 MW-class neutral beam injection

“Norman” is named in honor of Norman Rostoker. This device has achieved plasma temperatures above 75 million degrees and confinement times exceeding 30 milliseconds—record performance for an FRC device.

The next-generation device “Copernicus” aims to demonstrate D-T level performance, followed by “Da Vinci” for realizing the p-$^{11}$B reaction.

Collaboration with Google AI

TAE is collaborating with Google’s AI research team to optimize plasma control using machine learning. They have developed a method called the Optometrist algorithm, efficiently exploring optimal operating parameters that would be difficult for humans to discover intuitively.

This approach trains neural networks on thousands of experimental data points to predict conditions for the next experiment. Optimization speed has significantly improved compared to traditional trial-and-error approaches.

Tokamak Energy

Company Overview

Tokamak Energy, based in Milton Park near Oxford, UK, was founded in 2009. Founding members include researchers from START (Small Tight Aspect Ratio Tokamak) and MAST at the Culham Laboratory.

In 2024, the company completed a $230 million Series D funding round, bringing total funding to approximately$500 million. Major investors include Legal & General and Chevron.

Spherical Tokamak

Tokamak Energy’s technical distinction is the combination of spherical tokamak (ST) and HTS magnets.

While conventional tokamaks have a “doughnut” shape, spherical tokamaks have a shape closer to an “apple,” with a smaller aspect ratio (ratio of major to minor radius). The aspect ratio $A = R_0/a$ is typically 3-4 for conventional tokamaks, but 1.3-1.5 for spherical tokamaks.

The advantage of low aspect ratio is achieving higher beta values. The toroidal beta limit is given by:

$$\beta_t \leq \beta_N \frac{I_p}{a B_t}$$

($\beta_N$ is normalized beta). In spherical tokamaks, geometric effects increase $\beta_N$, allowing confinement of higher density plasma at the same size.

Additionally, spherical tokamaks naturally have a higher fraction of bootstrap current. Bootstrap current $I_\text{bs}$ is current spontaneously driven by density gradients:

$$I_\text{bs} \propto \varepsilon^{1/2} \frac{dp}{dr}$$

($\varepsilon = a/R_0$ is inverse aspect ratio). A high bootstrap current fraction reduces the need for external current drive and facilitates steady-state operation.

ST40 and ST80-HTS

Tokamak Energy has progressively scaled up its devices:

• ST25 (2013): Proof of concept
• ST25-HTS (2015): First use of HTS magnets
• ST40 (2017-present): Achieved plasma temperature of 100 million degrees (8.6 keV)

ST40 achieved a plasma temperature of 100 million degrees in 2022, a first for a private fusion company.

The next-generation device “ST80-HTS” is currently under construction, with operation targeted for 2026. This device combines high fields from HTS magnets with the high beta of spherical tokamaks, with a goal of demonstrating $Q > 1$.

Roadmap to Commercial Reactor

Tokamak Energy is targeting commercial power generation in the 2030s. The company’s roadmap includes:

1. ST80-HTS (2026-): $Q > 1$ demonstration
2. Pilot plant (early 2030s): Grid connection
3. Commercial reactor (late 2030s): Economic power generation

The UK government supports spherical tokamak development through the STEP (Spherical Tokamak for Energy Production) program, and Tokamak Energy has become a key player in this ecosystem.

General Fusion

Company Overview

General Fusion, based near Vancouver, Canada, was founded in 2002. Founder Michel Laberge was a laser inertial confinement researcher but developed Magnetized Target Fusion (MTF) seeking a more practical approach.

As of 2025, total funding is approximately $300 million, with investors including Jeff Bezos, the Canadian government, and Shopify founder Tobias Lutke.

Magnetized Target Fusion (MTF)

Magnetized Target Fusion, employed by General Fusion, is a hybrid approach between magnetic confinement fusion (MFE) and inertial confinement fusion (ICF).

In MTF, a plasma target confined by magnetic fields is first formed, then mechanically compressed to heat and compress the plasma to fusion conditions. During compression, adiabatic heating follows:

$$T \propto \rho^{\gamma-1}$$

($\gamma$ is the heat capacity ratio). Energy can be efficiently delivered through mechanical compression while suppressing plasma thermal conduction losses through magnetic confinement.

In General Fusion’s approach, a vortex of liquid metal (steel-lithium alloy) is formed, and plasma is injected into its center. Then, numerous pistons simultaneously compress the liquid metal, heating the plasma to fusion temperatures.

Advantages of this approach:

1. Liquid metal acts as a barrier between plasma and wall, mitigating materials issues
2. Liquid metal functions as a blanket for tritium breeding
3. Piston compression is an application of existing technology, cheaper than large lasers
4. Pulsed operation avoids the difficulty of steady-state plasma control

Physics of Liquid Metal Compression

The behavior of liquid metal during compression is described by fluid dynamics. The continuity equation for an incompressible fluid:

$$\nabla \cdot \mathbf{v} = 0$$

and the equation of motion:

$$\rho\left(\frac{\partial \mathbf{v}}{\partial t} + \mathbf{v} \cdot \nabla \mathbf{v}\right) = -\nabla p + \mu \nabla^2 \mathbf{v}$$

allow analysis of the liquid metal flow and plasma compression process.

When the cavity radius $R$ contracts with time, the relationship between its velocity $\dot{R}$ and pressure $p$ is given by the Rayleigh-Plesset equation:

$$R\ddot{R} + \frac{3}{2}\dot{R}^2 = \frac{p_\infty - p(R)}{\rho}$$

In General Fusion’s design, hundreds of pistons are driven synchronously, achieving more than 10-fold volume compression on millisecond timescales.

Demonstration Plant LM26

General Fusion is building a demonstration plant called “LM26” on the grounds of the Culham Laboratory in the UK. This plant will conduct integrated demonstrations of liquid metal technology and test full-scale compression systems.

Operation is targeted for 2026, and if successful, the company plans to proceed with pilot plant construction in the 2030s.

Helion Energy

Company Overview

Helion, founded in Washington State in 2013, employs the FRC approach developed by founders David Kirtley and Chris Pihl.

In January 2025, the company raised $425 million, bringing total funding to approximately$1 billion. OpenAI CEO Sam Altman personally invested $375 million, making him the largest individual investor.

In May 2023, Helion signed a power purchase agreement with Microsoft. This is the world’s first commercial contract to purchase electricity from a fusion power plant, targeting supply of more than 50 MW of electricity starting in 2028.

Pulsed Fusion and Direct Energy Conversion

Helion’s approach is called “pulsed fusion,” achieving fusion conditions by colliding FRC plasmas at high speed.

The kinetic energy of plasma is:

$$E_k = \frac{1}{2}mv^2$$

When FRC plasmas are accelerated to several hundred km/s and collided, kinetic energy is converted to thermal energy, reaching fusion temperatures.

Helion’s unique feature is “direct energy conversion.” Conventional fusion power plants use heat generated from fusion to drive steam turbines for electricity generation. However, Helion aims to obtain electricity directly through electromagnetic induction from time-varying magnetic fields.

By Faraday’s law:

$$\mathcal{E} = -\frac{d\Phi_B}{dt}$$

A time change in magnetic flux $\Phi_B$ produces an electromotive force $\mathcal{E}$. In Helion’s device, the expanding FRC plasma after fusion reactions induces magnetic flux changes in surrounding coils, generating electricity.

This approach theoretically achieves efficiencies above 90%, significantly higher than the 30-40% of turbine generation.

Deuterium-Helium-3 Reaction

Helion’s target fuel is D-$^3$He:

$$\text{D} + {^3\text{He}} \rightarrow {^4\text{He}} + p + 18.3 \text{ MeV}$$

The products of this reaction are only charged particles (alpha particles and protons), with no neutron generation. Since charged particles can be directly decelerated by magnetic fields, they are well-suited for direct energy conversion.

However, $^3$He is extremely rare on Earth. Helion plans to address this problem by self-producing $^3$He using D-D reactions:

$$\text{D} + \text{D} \rightarrow {^3\text{He}} + n + 3.27 \text{ MeV}$$

Part of the D-D reactions produce $^3$He, which is recovered and used as fuel for D-$^3$He reactions.

Polaris

In 2024, Helion began operating its 7th generation prototype device “Polaris.” Polaris has the following objectives:

• Demonstration of net energy ($Q > 1$)
• Integrated testing of direct energy conversion system
• Technology validation toward commercial reactors

Achieving the power supply contract with Microsoft requires successful technology demonstration with Polaris.

First Light Fusion

Company Overview

First Light Fusion, spun off from Oxford University, was founded in 2011. The company is developing a “projectile fusion” approach, a variant of inertial confinement fusion (ICF).

Total funding is approximately $200 million, with investors including IP Group, OSI, Tencent, and Legal & General, which also invests in Tokamak Energy.

Projectile Fusion

In laser inertial confinement, hundreds of laser beams compress the target, but laser facilities are enormous and expensive. First Light Fusion uses physical “projectiles” instead of lasers to compress targets.

When a projectile accelerated by an electromagnetic gun impacts the target, a shock wave is generated. The shock wave pressure is given by the Rankine-Hugoniot relation:

$$p_2 - p_1 = \rho_1 U_s (u_2 - u_1)$$

Here $U_s$ is shock wave velocity and $u$ is material velocity. A properly designed target (“amplifier”) converges the shock wave to generate extremely high pressure and temperature in the fuel region.

The fusion gain from compressed fuel is evaluated as:

$$G = \frac{E_\text{fusion}}{E_\text{projectile}}$$

First Light Fusion aims to achieve high gain through optimization of target design.

Machine 3 and Neutron Generation

In April 2022, First Light Fusion successfully generated neutrons from fusion reactions with Machine 3. This is the world’s first achievement for an inertial fusion approach without using lasers.

Neutron detection was confirmed by multiple independent methods:

1. Neutron time-of-flight detector
2. Activation analysis (indium foil)
3. Fission chamber

This demonstration confirmed the basic principles of the projectile fusion approach.

Target Design

One of First Light Fusion’s competitive advantages lies in target design. Conventional ICF targets were designed assuming precise laser illumination, but projectile impact requires different designs.

The company designs targets as “amplifiers.” The outer shell absorbs the kinetic energy of the projectile, converging shock waves through a complex internal structure to compress the central fuel capsule.

Target optimization requires large-scale hydrodynamic simulations, and First Light Fusion utilizes high-performance computing.

Commercialization Approach

In First Light Fusion’s commercial power plant concept, targets and projectiles are continuously supplied, generating fusion pulses. The power generation cycle is as follows:

1. Accelerate projectile with electromagnetic gun
2. Impact target, fusion reaction
3. Recover generated heat with liquid metal
4. Generate electricity with steam turbines

Compared to laser facilities, electromagnetic guns are inexpensive and scalable. Mass production costs of targets are key to economics, and the company is developing low-cost manufacturing methods using 3D printing technology.

Zap Energy

Company Overview

Zap Energy, founded in 2017, is based in Everett, Washington. Founders Professor Uri Shumlak (University of Washington) and Professor Brian Nelson have over 20 years of experience in sheared-flow Z-pinch research.

Total funding is approximately $250 million, with investors including Chevron, Lux Capital, DCVC, and Addition (Lee Fixel’s fund).

Sheared-Flow Z-Pinch

Z-pinch is one of the oldest fusion confinement approaches. When an axial current flows through plasma, an azimuthal magnetic field is generated according to Ampere’s law:

$$\oint \mathbf{B} \cdot d\mathbf{l} = \mu_0 I$$

This magnetic field compresses the plasma inward (pinch effect):

$$\mathbf{J} \times \mathbf{B} = \frac{J_z B_\theta}{r}\hat{r}$$

However, conventional Z-pinch has been plagued by sausage and kink instabilities. These magnetohydrodynamic (MHD) instabilities cause the plasma to collapse within microseconds.

Zap Energy’s innovation is “sheared flow.” By imparting an axial velocity gradient (shear) to the plasma, instabilities can be suppressed. The condition for sheared-flow stabilization is:

$$\left|\frac{dv_z}{dr}\right| > \frac{k v_A}{2}$$

($v_A$ is Alfven velocity, $k$ is wave number). With sufficient shear, MHD instability growth can be suppressed and plasma can be confined for extended periods.

Technical Advantages

The greatest advantage of the Z-pinch approach is simplicity. It does not require complex magnet systems like tokamaks or stellarators, consisting only of a linear plasma chamber and power supply.

This enables:

1. Significant reduction in manufacturing costs
2. Ease of maintenance and servicing
3. Potential for miniaturization and modularization
4. No superconducting materials required

Zap Energy aims for a “factory-manufacturable fusion reactor” leveraging this simple structure.

FuZE Device

Zap Energy’s experimental device “FuZE” (Fusion Z-pinch Experiment) is used to study the physics of sheared-flow stabilized Z-pinch in detail. FuZE has reported the following achievements:

• Plasma currents above 16 kA
• Stable confinement for tens of microseconds
• Electron temperatures above 30 keV
• Ion temperatures above 20 keV

In 2022, Zap Energy confirmed neutron generation from fusion reactions. These are thermonuclear neutrons from D-D reactions, demonstrating the company’s technical progress.

The next-generation device “FuZE-Q” aims for $Q = 1$, with a target of achievement in the late 2020s.

Type One Energy

Company Overview

Type One Energy, founded in 2019, is one of the few private companies adopting the stellarator approach. Based in Madison, Wisconsin, its founding members include researchers from the University of Wisconsin and the Max Planck Institute for Plasma Physics (IPP) in Germany.

In 2024, the company completed a major $290 million funding round, bringing total funding to approximately$350 million. Investors include General Atomics, Qualcomm founder Irwin Jacobs, Bill Gates, and Breakthrough Energy Ventures.

Physics of Stellarators

Stellarators form magnetic confinement structures using only external coils. While tokamaks require plasma current, stellarators achieve confinement without plasma current.

Stellarator magnetic configurations have three-dimensionally twisted shapes. These shapes are optimized to satisfy the following conditions:

1. Particle confinement: Particles should not escape by drifting
2. MHD stability: Plasma should be stable
3. Reduction of neoclassical transport: Minimize particle and energy losses

Quasi-symmetry is an important concept in stellarator optimization. When the magnetic field magnitude $|B|$ is independent of certain coordinates, particle confinement in that direction is improved. Type One Energy adopts quasi-axisymmetry.

In quasi-axisymmetric magnetic fields:

$$|B| = B(\psi, \theta - N\phi)$$

Here $\psi$ is the flux function, $\theta$ is the poloidal angle, $\phi$ is the toroidal angle, and $N$ is the period number. Under this condition, neoclassical transport coefficients are reduced to levels comparable to tokamaks.

Combining HTS and Stellarators

Type One Energy’s technical innovation is the combination of HTS magnets with stellarators.

Traditionally, the complex three-dimensional coil shapes of stellarators have been a major manufacturing challenge. However, HTS tape is flexible and easy to process into complex shapes. Furthermore, the high fields of HTS enable device compactification, reducing manufacturing costs.

The company plans to utilize additive manufacturing (3D printing) technology to fabricate complex coil support structures.

Commercial Reactor Design “Infinity”

Type One Energy’s commercial reactor concept “Infinity One” has the following features:

• High fields (above 10 T) from HTS magnets
• Optimized quasi-axisymmetric stellarator configuration
• Electrical output: ~450 MW
• Steady-state operation (no plasma current required)

The greatest advantage of stellarators is “steady-state operation.” Tokamaks require additional energy input to maintain plasma current, but stellarators form magnetic fields with external coils only, enabling steady-state operation in principle.

This is an important advantage for power plant operation. Continuous operation rather than pulsed operation improves power supply stability and capacity utilization.

Commercial operation is targeted for the mid-2030s.

Comparison of Approaches

Overview of Technical Approaches

Technical approaches adopted by fusion startups can be broadly categorized as follows:

Approach	Companies	Key Features
Compact Tokamak (HTS)	CFS, Tokamak Energy	Compactification through high fields
Field-Reversed Configuration (FRC)	TAE, Helion	High beta, potential for direct conversion
Stellarator	Type One Energy	Steady-state operation, no plasma current needed
Magnetized Target Fusion (MTF)	General Fusion	Mechanical compression, hybrid approach
Z-Pinch	Zap Energy	Simple structure, low cost
Projectile Fusion (ICF variant)	First Light Fusion	ICF without lasers

Fuel Selection and Neutron Issues

Fuel selection significantly influences each company’s strategy:

Company	Fuel	Neutron Generation	Notes
CFS	D-T	High	Conventional optimal fuel
Tokamak Energy	D-T	High	Conventional optimal fuel
General Fusion	D-T	High	Shielded by liquid metal
First Light Fusion	D-T	High	Inertial confinement
Zap Energy	D-T	High	Simple structure
TAE	p-$^{11}$B (target)	Low	Requires high temperature
Helion	D-$^3$He	Low	$^3$He supply challenges
Type One Energy	D-T	High	Stellarator

The D-T reaction has the largest cross-section and enables fusion at the lowest temperature. Fusion gain is given by:

$$Q_\text{DT} \propto \frac{n^2 \langle\sigma v\rangle_\text{DT}}{P_\text{loss}}$$

and the $\langle\sigma v\rangle$ for D-T peaks around 10 keV.

On the other hand, fuels that do not generate neutrons (advanced fuels) mitigate materials issues but require orders of magnitude higher temperatures to achieve. TAE’s p-$^{11}$B and Helion’s D-$^3$He are tackling this challenge.

Commercialization Schedules

Commercialization schedules announced by each company:

Company	Demo Reactor	Commercial Power Start	Notes
CFS	2025 (SPARC)	Early 2030s (ARC)	Microsoft/Google contracted
Helion	2024 (Polaris)	2028	Microsoft contracted, most aggressive
Tokamak Energy	2026 (ST80-HTS)	2030s	UK government support
General Fusion	2026 (LM26)	Late 2030s	Demo reactor in UK
TAE	Late 2020s	2030s	Starting from D-T phase
Zap Energy	Late 2020s	2030s	$Q = 1$ target
First Light Fusion	Late 2020s	2030s	Pilot construction
Type One Energy	Around 2030	Mid-2030s	Stellarator

While these schedules may be optimistic, each company is making rapid progress toward specific milestones.

Investment Trends and Funding

Overview

Private investment in fusion is accelerating in 2025, with $1.16 billion raised in the first quarter alone, on pace to exceed$3 billion annually. According to the Fusion Industry Association (FIA), cumulative investment has reached approximately $9.8 billion as of 2025.

The investor composition is as follows:

1. Venture capital: Lux Capital, DCVC, Breakthrough Energy Ventures, Khosla Ventures
2. Tech companies/founders: Google, Microsoft, Jeff Bezos, Sam Altman, Bill Gates
3. Energy companies: Chevron, Equinor, Eni
4. Sovereign wealth funds: Public funds from various countries
5. Institutional investors: Legal & General, Tiger Global

Major Funding Rounds

Major funding rounds in 2024-2025:

• Pacific Fusion (2024): $900 million Series A (laser inertial confinement)
• CFS (August 2025): $863 million Series B2
• Helion (January 2025): $425 million
• Type One Energy (2024): $290 million Series B
• Tokamak Energy (2024): $230 million Series D

Pacific Fusion’s $900 million raise is the largest ever for an inertial confinement startup, reflecting increased investor interest following NIF’s ignition success (2022).

Enterprise Valuations

Estimated enterprise valuations of major companies:

Company	Valuation	Total Funding
TAE Technologies	$6 billion	Over $1.2 billion
Commonwealth Fusion Systems	Over $5 billion	$3 billion
Helion Energy	Undisclosed (est. $3-5 billion)	$1 billion
Tokamak Energy	Undisclosed (est. $1-1.5 billion)	$500 million

Fusion startup valuations continue to rise despite high technical risk. This is due to the urgency of climate action and increased investor confidence from some companies achieving technical milestones.

Government Support

In addition to private investment, governments in various countries are strengthening support for fusion:

Country/Region	Annual Budget	Key Initiatives
USA	$1.5 billion	DOE milestone program, public-private matching
UK	£300 million	STEP program, UKAEA collaboration
Germany	€280 million/year (€1.4 billion over 5 years)	W7-X continuation, private support
Japan	~¥50 billion	QST, J-Fusion
EU	ITER contribution, Horizon Europe	Focused on large projects
China	Multi-billion dollar scale	EAST successor, private support starting

The U.S. Department of Energy (DOE) “milestone program” provides federal funding when private companies achieve technical targets—a good example of public-private partnership. CFS and TAE are among the recipients.

Japanese Startups

Kyoto Fusioneering

Company Overview and Strategy

Founded in 2019, Kyoto Fusioneering is a Kyoto University spinout that has adopted a unique strategy of specializing in peripheral equipment rather than the fusion reactor core itself.

As a “plant engineering” company, it operates a business model of supplying technology and equipment to fusion reactor developers worldwide. It occupies a position similar to “shovel sellers” (merchants who sold picks and shovels during the Gold Rush).

In September 2025, the company raised ¥6.75 billion, bringing total funding to approximately ¥9.4 billion. The company is valued at ¥72.1 billion, making it the largest fusion startup in Japan.

Product Lineup

Kyoto Fusioneering’s main products:

Gyrotron A microwave generation device for plasma heating. Used for Electron Cyclotron Resonance Heating (ECRH), it generates microwaves at specific frequencies absorbed in plasma.

The electron cyclotron frequency is:

$$\omega_\text{ce} = \frac{eB}{m_e}$$

For typical tokamak magnetic fields (2-5 T), this corresponds to approximately 50-140 GHz. Kyoto Fusioneering’s gyrotrons cover this frequency range and heat plasma with high efficiency.

Blanket A structure covering the fusion reactor wall with two functions:

1. Heat recovery: Slowing neutrons generated from fusion and converting to thermal energy
2. Tritium breeding: Generating tritium through reactions between lithium and neutrons

$${^6\text{Li}} + n \rightarrow {^4\text{He}} + T + 4.8 \text{ MeV}$$ $${^7\text{Li}} + n \rightarrow {^4\text{He}} + T + n' - 2.5 \text{ MeV}$$

The Tritium Breeding Ratio (TBR) is directly related to reactor self-sufficiency, with TBR > 1.05 required.

Heat Exchanger Equipment that transfers high-temperature heat recovered from blankets to the power generation cycle. Design must accommodate the high heat fluxes (several MW/m²) unique to fusion.

Customers and Track Record

Kyoto Fusioneering has already delivered equipment to multiple customers:

• UK Atomic Energy Authority (UKAEA): Gyrotron for MAST Upgrade
• CFS: Blanket/divertor design collaboration for SPARC
• General Atomics: Equipment for DIII-D

In April 2025, the company established a subsidiary “Starlight Engine” for power generation demonstration, targeting demonstration in the late 2030s. This signifies a strategic shift to venture beyond peripheral equipment into core reactor technology.

Other Japanese Companies

Helical Fusion

A startup founded in 2021 leveraging helical technology from the National Institute for Fusion Science (NIFS). Based on knowledge from the Large Helical Device (LHD), it aims to develop compact helical reactors.

The helical approach is a type of stellarator that provides magnetic confinement without plasma current. The initiative applies technology and operational experience cultivated at LHD to private development.

EX-Fusion

A startup from Osaka University’s Institute of Laser Engineering, founded in 2022. It is developing laser fusion, aiming for practical inertial confinement fusion using “high-repetition-rate lasers.”

Based on research at Osaka University’s GEKKO XII, it pursues practical application in the private sector.

Nihon Nuclear Fusion Energy (formerly NT-Tao)

A startup founded in 2019 developing FRC and magnetic mirror configurations. Starting from basic physics research in magnetic confinement, it is exploring paths to practical reactors.

J-Fusion and the Industrial Ecosystem

In March 2024, the “Fusion Energy Industry Council (J-Fusion)” was established, advancing collaboration in Japan’s fusion industry. Participating companies include:

• Fusion startups
• Heavy electrical manufacturers (Mitsubishi Heavy Industries, Hitachi, Toshiba, etc.)
• Materials manufacturers
• Engineering companies

They are cooperating on supply chain development, human resource development, and regulatory response.

Relationship Between Private and Public Research

Complementary Roles

Private ventures and public research institutions have a complementary rather than adversarial relationship.

Strengths of public research institutions:

• Accumulation of fundamental research (decades of data)
• Large experimental facilities (ITER, JT-60SA, W7-X, etc.)
• Long-term perspective on human resource development
• Influence on regulatory framework development
• Platform for international cooperation

Strengths of private companies:

• Rapid decision-making and innovation
• Technology development toward commercialization
• Supply chain construction
• Progress driven by investor commitments
• Collaboration with existing industries

Flow of Knowledge and Talent

Many fusion startups are spinoffs from universities and national laboratories:

Company	Origin Institution
CFS	MIT PSFC
Tokamak Energy	Culham Laboratory
Type One Energy	University of Wisconsin, IPP
First Light Fusion	Oxford University
Kyoto Fusioneering	Kyoto University
Helical Fusion	NIFS
EX-Fusion	Osaka University

This flow is not one-way; technology developed at startups is sometimes fed back to public research. For example, CFS’s HTS magnet technology continues to be refined through joint research with MIT.

National Policies and Private Support

Governments in various countries are strengthening support for private fusion:

United States

• 2022 “Ten-Year Vision for Fusion Energy Sciences” formulation
• DOE milestone-based grant program
• Development of regulatory framework (NRC)

United Kingdom

• STEP (Spherical Tokamak for Energy Production) program
• UKAEA Fusion Technology Facility (RACE)
• Regulatory sandbox system

Japan

• 2023 “Fusion Energy Innovation Strategy”
• Collaboration with QST (National Institutes for Quantum Science and Technology)
• J-Fusion establishment support
• Regulatory review (consistency with current nuclear reactor regulation law)

Relationship with ITER

ITER is a massive project of international cooperation, playing a different role from private companies. ITER’s objectives are:

1. Physics demonstration of burning plasma ($Q \geq 10$)
2. Technical demonstration of integrated fusion systems
3. Establishment of an international technology foundation

Private companies aim for faster commercialization while leveraging ITER’s results. Both are not competitors but different approaches toward the common goal of achieving fusion.

Many startup executives position ITER as “proof that fusion works,” while their own companies “commercialize it faster,” recognizing this division of roles.

Technology Transfer and Intellectual Property

Technology transfer from universities and research institutes to startups involves important considerations regarding intellectual property (IP). Common patterns include:

1. License agreements: University retains IP, startup pays licensing fees
2. IP transfer: Startup acquires IP at founding
3. Joint development: Sharing IP for new developments

CFS is licensed for related IP from MIT while also providing research funding to MIT. This bidirectional relationship creates a virtuous cycle between academic research and private development.

Challenges and Outlook

Technical Challenges

Major technical challenges facing private companies:

Plasma Confinement Improving the fusion triple product $nT\tau_E$ remains the greatest challenge. Different approaches present different challenges, but demonstration of high-performance confinement is universally needed.

Materials Issues The 14.1 MeV neutrons from D-T reactions damage structural materials. When neutron damage (dpa: displacements per atom) exceeds several tens of dpa, material properties degrade and replacement becomes necessary.

The first wall and divertor are exposed to particularly harsh environments. Heat loads reach:

$$q \sim 10-20 \text{ MW/m}^2$$

This heat flux exceeds that of rocket engine nozzles.

Tritium Self-breeding of tritium is essential for D-T fueled reactors, but blanket designs achieving TBR > 1 have not yet been demonstrated. ITER plans to verify tritium breeding with Test Blanket Modules (TBM).

Steady-State Operation Maintaining fusion continuously rather than in pulses is an essential condition for power plants. Steady-state current drive is a challenge for tokamaks, where stellarators have an advantage.

Economic Feasibility

The economics of fusion power plants are determined by the following factors:

$$\text{LCOE} = \frac{\text{Capital Cost} \times \text{CRF} + \text{Annual Operating Cost}}{\text{Annual Electricity Generation}}$$

(CRF: Capital Recovery Factor)

The LCOE (Levelized Cost of Electricity) for fusion is currently unknown, but to be competitive with solar and wind, targets below $50/MWh are set.

Keys to cost reduction:

• Device compactification through HTS magnets
• Economies of scale (modular design)
• Shortened construction periods
• Improved operational efficiency

Regulation and Licensing

Regulatory frameworks for fusion power plants are underdeveloped in many countries. Applying nuclear fission regulations directly could result in over-regulation, and rational regulation reflecting fusion’s unique risk profile (no runaway reactions, no high-level waste) is needed.

The U.S. NRC (Nuclear Regulatory Commission) began considering a fusion-specific regulatory framework in 2023. The UK has announced a policy to regulate fusion in a separate category from nuclear reactors.

Social Acceptance

Fusion contains the word “nuclear,” raising concerns about social resistance due to confusion with nuclear fission. However, fusion’s risk profile is fundamentally different from fission:

1. Runaway (meltdown) is physically impossible
2. No high-level radioactive waste is produced
3. Diversion to nuclear weapons is difficult

Science communication that accurately conveys these differences is important.

Outlook for the 2030s

The 2030s will be a critical period for fusion commercialization. Key milestones:

• 2025-2026: CFS SPARC first plasma, Tokamak Energy ST80-HTS operation
• 2028: Helion commercial power start (target)
• Early 2030s: CFS ARC, ITER full power operation
• Mid-2030s: Multiple companies’ commercial reactor operation

If these are achieved, fusion could play a role in electricity supply by the 2040s. However, unexpected difficulties are inherent in technology development, and schedule delays are quite possible.

What’s important is that multiple approaches are proceeding in parallel. Competition among different approaches—tokamak, stellarator, FRC, MTF, Z-pinch, ICF—increases the probability that one will succeed.

Conclusion

The rise of private fusion ventures is bringing new vitality to fusion energy development. The combination of advances in HTS magnet technology, investment appetite for climate action, and structural advantages of private companies enabling rapid development is beginning to overturn the pessimism that “fusion is always 30 years away.”

As of 2025, approximately 40 fusion startups are active worldwide, with nearly $10 billion invested. Leader companies such as CFS, TAE, Helion, and Tokamak Energy are racing toward commercialization with different technical approaches.

At the same time, challenges abound. Demonstration of plasma confinement, materials issues, tritium breeding, economics, regulatory frameworks—challenges span many areas. Critics suggest the commercialization schedules announced by each company may be too optimistic.

However, through the complementary relationship between private and public institutions, flow of technology and talent, and strengthened government support, the ecosystem for achieving fusion energy is steadily growing.

As the “ultimate clean energy,” fusion has the potential to solve energy problems in the age of climate change. Rapid development by private companies and deep accumulation of knowledge by public research—when these two wheels mesh, fusion energy will advance from “dream” to “reality.”

Related Topics

• Future Outlook: Overview - Future vision of fusion energy
• ITER Project - Large tokamak through international cooperation
• JT-60SA Project - Advanced tokamak through Japan-EU collaboration
• Tokamak Approach - Mainstream magnetic confinement method
• Stellarator/Helical Approach - Alternative magnetic confinement method