Clarity and transparency on the path to fusion energy

Fusion energy is attracting unprecedented levels of enthusiasm and investment, at home and abroad.

This is for good reason. Fusion energy holds the potential to unlock a new era of prosperity. Abundant, reliable, on-demand energy has always been key to technological progress, everywhere – and now, in the age of AI and electrification, the largest U.S. grid operator is predicting a 60GW shortfall over the next decade.

At the same time, as interest in the field grows, we recognize the need to be better as an industry at providing the scientific and technical basis to understand our progress, so that others can independently assess what’s hype and what’s real.

In 2024, Bob Mumgaard, CEO of Commonwealth Fusion Systems, published Building Trust in Fusion Energy, which laid out CFS’ perspective on how to evaluate progress in the field.

The goal of this letter is to similarly share Pacific Fusion’s perspective on what the key milestones are on the way to commercial power, including quantitative metrics for comparing progress across companies. We then describe Pacific Fusion’s own progress and plans along that path.

Evaluating progress toward affordable fusion power 

In our view, a company’s path to affordable fusion power must start with a firm foundation and progress through five key milestones. 

Foundation: Fusion Technology and Lawson Criteria. The foundation for the milestones is (1) the proposed fusion technology, and (2) the corresponding Lawson criteria required for scientific gain and net facility gain for that technology. We encourage all fusion companies to provide a clear description of this information in a peer-reviewed paper so that others can independently assess the advantages and risks of the approach.

• The Lawson criteria, first articulated in 1955 by physicist John D. Lawson, defines the scientific bar for a useful fusion energy system: a plasma must exceed a minimum combination of temperature, density, and confinement time, captured in the Lawson criteria.
• Different fusion concepts have different Lawson criteria requirements for achieving milestones (2) and (3) below. For most D-T fusion approaches, though, the thresholds are within a factor of ~10. 

Milestones: There are five key milestones on the path toward commercial fusion power. 

For each company or approach, we encourage prospective investors, commentators, and journalists to evaluate: 

• Which milestones below have already been achieved — that is, demonstrated experimentally as shown in a peer-reviewed publication?
• For milestones not yet achieved: What is the evidence that indicates these milestones can be achieved, and what are the remaining challenges to overcome? 

Pacific Fusion’s thesis and progress

Below, we describe progress toward these milestones for Pacific Fusion’s fusion concept.

Foundation: Achieved and Published ✅

We are building a pulser-driven inertial fusion system, most similar to the Z Facility at Sandia National Laboratories. It is described in detail, together with the relevant Lawson criteria, in this paper which we published last year in the peer-reviewed journal Physics of Plasmas.

Milestone 1, Scientific Proof of Concept: Achieved and Published ✅

Experiments at the Z facility at Sandia National Laboratories reported in 2022 achieving the second-highest Lawson triple product, L, exceeding 10²¹ keV-s/m³. 

Milestones 2 and 3, Scientific Gain and Net Facility Gain: On track for 2030

We founded Pacific Fusion in 2023 because a series of breakthroughs in 2022 at the U.S. National Laboratories opened a practical path to rapidly achieve milestones (2) and (3), with a sufficiently affordable and scalable system to achieve milestones (4) and (5).

Milestone 2: Scientific Gain. Scientific gain is a statement about the fusion reaction itself. It means that fusion energy released by the fuel exceeds the energy that was delivered to the fuel. Work at the National Laboratories has defined the precise conditions we need to achieve.

• How do we know?
  • NIF’s demonstration of controlled fusion ignition in December 2022 experimentally demonstrated, in a peer-reviewed paper, that inertial fusion can achieve ignition (and far exceed scientific gain) with a triple product of ~10²² keV-s/m−³. They demonstrated it using a laser-driven inertial system.
• The challenge:
  • The NIF was not designed for fusion energy and is too inefficient to achieve net facility gain (milestone 3).

Milestone 3: Net Facility Gain. To achieve Net Facility Gain in an inertial system, one must drive fuel to the required Lawson criteria with a sufficiently energy-efficient system. This can be done with a pulser-driven system. 

• How do we know?
  • Using the same simulation approach that accurately predicted ignition for NIF, high-fidelity simulations performed at Sandia National Laboratories show that ignition is achieved with current as low as 40-50 MA and net facility gain is achieved below 60 MA.
  • Experiments at the Z facility at Sandia National Laboratories confirm this works up to the maximum current that the Z-machine can currently drive through MagLIF targets – and demonstrated the second-highest Lawson criteria ever when they reported it in 2022. 
     
• The challenge: Nobody has yet built a machine that efficiently generates a ~60 MA current – and is affordable, practical, manageable and scalable enough to be a basis for cost-competitive power systems. This is the engineering problem that Pacific Fusion was founded in 2023 to solve.
  • We are building a modular, mass-manufacturable system consisting of ~156 identical units which together will drive a ~60 MA current across a fusion target efficiently enough to achieve net facility gain.
  • At the core of the system is a next-generation pulsed power driver known as the impedance-matched Marx generator (IMG), which was co-invented by Pacific Fusion Chief Technology Officer Keith LeChien. This innovation nearly doubles the efficiency of existing pulsed power fusion systems and reduces the required facility size by half. 
     
• Next milestone:
  • Our next major milestone is demonstrating that our core technology works as expected – that is, building one pulser module and demonstrating that it reliably produces the ~2 TW of peak power required to achieve this objective.⁴
  • After this demonstration, the remaining question will become how quickly we can build the remaining ~155 identical modules, demonstrate scientific gain, and then demonstrate net facility gain.

Milestones 4 and 5, Power Gain and Affordable Power

Net facility gain is a critical milestone — but it is not the end of the road. For fusion energy to realize its potential, fusion machines must be built in a way that also enables the rapid achievement of power gain and affordable power.

Power gain means the system generates more electrical power than it uses. Whereas net facility gain compares energy out to energy in, power gain requires building a system to convert the fusion energy into electricity and generate net power, accounting for any losses in this process. Considering the ~30-40% efficiencies of traditional heat engines and other power needs, achieving power gain requires achieving a net facility gain of ~3–4.

Affordable power depends on the capital, operating, and maintenance costs of the system, which determine the cost of electricity produced and whether that cost is competitive with alternatives. That means building:

• Modular systems: Modular systems (like Pacific Fusion’s) that can be built offsite and shipped offer a more practical path to scale and a faster path to low cost. The cost and speed advantages of modular systems are well documented: they can be built up to 10× cheaper and twice as fast as bespoke megaprojects.
   
• Systems with a clear path to safe and affordable operations and maintenance, including
  • Survivable plasma-facing surfaces,
  • A sustainable tritium economy,
  • Affordable radiation shielding for safe operations, and
  • For inertial systems, affordable and manufacturable targets.
     
• Systems whose deployment is not bottlenecked by grid infrastructure. Fusion machines must integrate with existing grid infrastructure and operate within today’s transmission constraints. 

Each of these items requires solving a whole new host of engineering challenges, which our team is committed to tackling pragmatically and early. In one recent example, we shared an important advance necessary to enable repetitive operation, by eliminating complex hardware and simplifying target design. 

A final note

Fusion’s promise is enormous – but it is hard. It combines the challenges of first-of-a-kind science and engineering with the complexity of large-scale industrial projects.  

And while there may be multiple paths to success, there are no shortcuts. For those evaluating the field – investors, policymakers, and journalists – the question to be asking is: who can show measurable, independently verifiable progress toward affordable power at scale?

Progress is easy to claim, but structured milestones and peer review make those claims credible. Together, they create a shared standard to strengthen credibility across the field.  

At Pacific Fusion, we are committed to sharing our progress openly and publishing our work whenever possible. Last year, we published four peer-reviewed papers outlining our technical roadmap and validating the simulations tools we use to guide experiments. We will continue to publish, present at conferences, and subject our work to rigorous review along the way. 

To achieve fusion’s potential, we must reduce technical and execution risk — and hold ourselves to a high bar of integrity in how we communicate progress. That discipline is the foundation on which fusion’s future will be built.   
 

References

¹L = temperature x density x energy confinement time. For scientific gain to occur, the fuel must both exceed a certain minimum temperature T_min and exceed the necessary L for the operating temperature. For simplicity, people often focus on the value of L at the minimum temperature. 

²For most D-T fusion approaches, this means a Lawson triple product above ~10¹⁹ keV-s/m³ with >1keV plasma temperatures. For approaches using other fuels the threshold is much higher. 

³ Only a small fraction of the energy stored in the system gets delivered to the target. 

⁴That’s a lot of power: it’s 4x larger than the average power provided by the entire US electric grid, during the duration of the pulse.