Physicists have been working to design fusion reactors, technologies that can generate energy via nuclear fusion processes, for decades. The successful construction of commercial fusion reactors relies on the ability to effectively confine charged particles with magnetic fields, because this in turn enables the control of high-energy plasma.

Researchers at Laboratorio Nacional de Fusión–CIEMAT in Madrid have developed a new family of magnetic fields that could be more efficient for confining particles in these devices without the need for complex equipment configurations. Their paper was published in Physical Review Letters. The work could be an important step toward the successful realization of fusion reactors.

José Luis Velasco is the first author of the paper. He said, “In the last years, there have been many initiatives proposing the design and construction of new experimental fusion devices and reactor prototypes. When these projects design the magnetic field that will confine the fusion plasma, practically all of them try to make the field ‘omnigenous.’ The fact that inspired our research is that the fusion community actually knew that it is possible to have magnetic fields that are quite far from being omnigenous but still display good plasma confinement (e.g., the Large Helical Device, an experimental device operating in Japan, and some old and recent numerical experiments in U.S.).”

In recent years, many physicists conducting research on nuclear fusion have focused their attention on omnigenous magnetic fields. Properties of these fields are well-documented. Velasco and his colleagues set about to investigate less understood magnetic fields that could inform the design of future stellarator reactors.

Velasco explained, “Our intuition was that, in these outliers, there was something interesting and useful to be learned about stellarator reactor design”.

In a stellarator, the electric currents passing through the coils generate a magnetic field organized into nested magnetic surfaces in the shape of a deformed doughnut. This magnetic field confines a plasma composed of deuterium and tritium hydrogen isotopes, as well as the charged alpha particles resulting from fusion.

For fusion reactions to occur, the plasma inside the stellarators needs to be hot enough. To raise plasma to these high temperatures, physicists must carefully design the magnetic fields used to confine particles. This process is known as “optimizing the stellarator.

Velasco said, “Optimizing the stellarator to make it omnigenous ensures that the particles that make up the plasma stay, along their trajectories, close to the same magnetic surface. Nevertheless, to achieve omnigenity, it is necessary to optimize the stellarator ‘as a whole.” In our work we have found that similarly good confinement properties are obtained if one ‘splits’ each magnetic surface of the stellarator into several pieces and optimizes each of them separately. Hence the name ‘piecewise omnigenous.’”

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The approach for optimizing stellarators proposed by Velasco and his colleagues could help to generate optimized magnetic fields for nuclear reactors more effectively. In contrast with previously proposed approaches, it also does not rely on complex plasma configuration and the use of sophisticated coils.

Velasco explained, “Designing and building an omnigenous field is not easy. In some cases, it may require complicated and expensive coils, which could endanger the whole project. An unfortunately extreme example of this was the National Compact Stellarator Experiment. Because there exists a vast variety of piecewise omnigenous magnetic fields, we are hopeful that some of them will be easier and/or cheaper to build.”

The recent work by this team of researchers may contribute to the future design of fusion reactors, by expanding the space of possible reactor configurations.

In their next studies, Velasco and his colleagues intend to systematically assess all the relevant physics properties of the piecewise omnigenous magnetic fields they uncovered, in order to determine whether they could compete with more conventional omnigenous magnetic fields.

Velasco added, “For instance, is the loss of energy due to turbulent processes too strong and how much simpler can we make the coils to comply with the technological requirements of a reactor? Answering these questions will require a lot of work, drawing on the expertise (in several areas: theory, experiment, technology, engineering, etc.) of many colleagues of the National Fusion Laboratory at CIEMAT and of other collaborators abroad.”

Laboratorio Nacional de Fusión–CIEMAT

Part 2 of 2 Parts (Please read Part 1 first)

LeChien explained, “The IMG was inspired by the need for a more practical, efficient, and reliable architecture for commercial fusion. As with a traditional Marx generator, it charges capacitors in parallel and discharges them in series. In this case, its triggering matches the speed of electromagnetic waves, so energy is delivered with about 90 percent efficiency. This boosts performance while cutting the size of the fusion system in half. The IMG uses lower-voltage components and standard materials, making it safer, easier to assemble, and more cost effective. The goal was to improve fusion performance while keeping the system simple, scalable, and practical for real-world power use.”

Each pulser module consists of stages (thirty-two for the demonstration system) connected in a series along a pulse tube. Each of the circular stages features multiple ‘bricks’ (ten per stage for the demonstration system) positioned around the circumference of the stage. Each brick consists of two capacitors and a switch. The electricity stored in the capacitors is released in pulses that travel through metallic pulse tubes toward the fusion chamber. The energy from multiple modules is funneled into two electrodes, which drive current through the target and electromagnetically compress it to trigger fusion.

Each pulser module has a diameter of about six feet and can deliver about two terawatts of peak power in a single fast pulse. PF expects its demonstration system to store about eighty megajoules of electrical energy and deliver more than sixty megaamperes in about one hundred nanoseconds.

That energy is directed to centimeter-scale deuterium-tritium fuel capsules. This is similar to laser-driven inertial confinement fusion, but this system has the ability to ‘magnetically squeeze’ the fuel inside a meter-scale fusion chamber surrounded by a deionized water tank for neutron shielding. PF’s founders believe their approach can expand the range of pressure and confinement time conditions under which fusion can be achieved.

The total footprint of the planned demonstration system is about two hundred and forty feet by two hundred and sixty feet. LeChien added that for a hypothetical future power plant, “We can tailor power plant size and capacity across a wide range, primarily by varying the designed target yield and/or repetition rate. One interesting combination would let us produce about two hundred and fifty megawatts with a very compact footprint of twenty-five acres or less.”

PF published a technical paper earlier this month on arXiv that details the company’s case for “affordable, manageable, practical, and scalable (AMPS) high-yield and high-gain inertial fusion.”

LeChien said that PF’s goal is “to generate the world’s lowest-cost firm power” and he noted that the company’s modular technology is “amenable to low-cost mass manufacturing with highly scalable supply chains. We combine estimates from detailed quote-informed costs of our demonstration system with average cost estimates of other fusion-related systems—the blanket, for example—and balance of plant.”

It requires a great deal of money to design affordable, scalable power sources. For PF, that includes the nine hundred million dollars of committed capital from investors, including venture capital firm General Catalyst, that was announced when PF emerged from ‘stealth mode’ in October of 2024. Those nine hundred million dollars are being released in tranches as the company reaches milestones.

LeChien added, “We’re pursuing federal funding opportunities to support our research, development, and demonstration efforts. Public-private partnerships are essential to accelerating fusion energy and building U.S. leadership in this field.”

LeChien continued, “About half of our technical team comes from the U.S. national labs, bringing deep fusion expertise. As we grow, we’re combining that foundation with talent from a wide range of fast-moving hard technology industries like aerospace and automotive. Our focus is on building a team that can move quickly, scale systems, and deliver real-world energy solutions.”

General Atomics

Part 1 of 2 Parts

Pacific Fusion (PF) and General Atomics (GA) recently announced plans to test Pacific Fusion’s pulser-driven inertial fusion energy concept, with commercial fusion power as the goal.

Keith LeChien is the PF cofounder and chief technology officer. He said, “We are building a fusion machine and testing all equipment—including components and a pulser module—at our PF test center. GA’s engineering expertise remains an important part of our progress, and we expect this collaboration to continue through future phases of development.”

Pacific Fusion is based in the Bay Area city of Fremont, Calif., where testing during last winter demonstrated that components of its pulser modules met performance and reliability expectations. Now, the company plans to test a production-scale pulser module designed to store electrical energy in a series of staged capacitors and deliver it in precisely controlled bursts. They will build one hundred and fifty-six such modules into a demonstration system by 2030. PF said earlier this month that it expects the machine to achieve net facility gain, generating more fusion energy out than all energy stored in the system.

LeChien explained, “Pacific Fusion is leading in pulsed magnetic fusion system design, including target physics, pulsed power, and mechanical engineering. GA has supported PF since our founding, contributing valuable engineering expertise. Their role has included system mechanical engineering analysis, benchtop prototype testing, and some infrastructure planning.”

Anantha Krishnan is the senior vice president of the General Atomics Energy Group. He said that GA’s expertise in computational modeling design, fusion science, and engineering “offers a powerful launchpad for fast-moving start-ups like Pacific Fusion.” Now that PF is progressing to module construction, GA’s role has expanded to include collaboration on full-scale fusion power plant components including system operations, cryogenics, manufacturing at production scale, and target fabrication.

GA is located in San Diego, about four hundred and fifty miles south of the PF headquarters in Fremont, California. GA has operated the DIII-D magnetic fusion tokamak there as a Department of Energy (DoE) user facility since 1986 and worked on DIII-D’s precursors since the 1950s. GA’s fusion expertise includes supplying components for ITER and manufacturing inertial fusion targets for the laser-driven National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). It also shared its own magnetic tokamak fusion pilot plant design in 2022.

Krishnan said, “General Atomics has developed significant capabilities in fusion science and technology over several decades of research and development. We are now applying these capabilities to help fusion energy companies tackle some of the toughest scientific and engineering challenges in achieving the goal of commercial fusion energy.”

Krishnan added, “GA’s business model is to provide our unique technical expertise and capabilities to enable our collaborators in the fusion energy industry to successfully bring fusion energy to the market. We work closely with a wide range of collaborators across the fusion landscape, including those focused on magnetic as well as inertial fusion.” LeChien is also the coinventor of the impedance-matched Marx generator (IMG) that the company’s power plant concept relies on.

Please read Part 2 next

Pacific Fusion

General Matter (GM) says it will use a novel, scalable, cost-competitive technology to address a ‘commercial bottleneck’ in the U.S. nuclear fuel cycle and that it will be shipping enriched uranium by the end of the decade.

GM was one of four companies selected in October of 2024 by the U.S. Department of Energy (DoE) to provide enrichment services to help establish a steady U.S. supply of high-assay low-enriched uranium (HALEU). According to information available at the time, the company was registered in California earlier in the year, with Scott Nolan named as its CEO. Nolan is a former SpaceX employee who is a partner at venture capital firm Founders Fund which was co-founded by billionaire investor Peter Thiel.

On the 14^th of April, the company announced itself on social media. It posted on X that “For the past year, General Matter has been incubated within Founders Fund, with a team from SpaceX, Tesla, Anduril, national labs, and the DOD. We are undertaking an engineering challenge which, if successful, will fundamentally improve the trajectory of our nation.”

Nolan said, “I spent over a year at Founders Fund searching for an American enrichment company to invest in, only to find there wasn’t one. So we built our own. General Matter is filling the US nuclear fuel gap. We are enriching uranium in America, and we will be shipping by the end of the decade”.

On the same day, Bloomberg reported that Peter Thiel is joining the board of GM. According to Bloomberg, the company has “built up a small operation in Los Angeles of roughly two dozen engineers, nuclear scientists and safety experts, pulling staff from national labs and the private sector.”

GM has not provided any details of its process for enriching uranium, but on the 2^nd of December last year, Nolan submitted a Letter of Intent to the U.S. Nuclear Regulatory Commission (NRC) in anticipation of a “forthcoming application for the necessary licenses to support the production and handling of High-Assay, Low-Enriched Uranium (HALEU)”.

The letter notes that “General Matter has been awarded an Indefinite Delivery/Indefinite Quantity (IDIQ) contract by the Department of Energy’s Office of Nuclear Energy (DOE-NE) under Solicitation No. 89243223RNE000031. This award specifically supports the DOE-NE’s strategic objectives of securing a domestic supply chain of HALEU to support the continued development of advanced reactors and to strengthen US leadership in nuclear technology. As a DOE-NE HALEU IDIQ awardee, General Matter’s anticipated scope of responsibility under future task orders includes the enrichment, storage, and transportation of HALEU. These operations are critical to meeting the growing demand for enriched uranium necessary to support both domestic and international markets, with an emphasis on maintaining safety and security standards.”

HALEU contains between five and 20 percent of fissile uranium-235 and will be required to meet the fuel needs of many of the advanced reactor designs that are currently being developed.

Information submitted to the NRC with the Letter of Intent is classed as ‘proprietary and confidential’, with the company saying, “Years of cumulative effort have gone into the work supporting this content, and given the innovative and differentiated insights generated by the work, others would need to expend great effort to duplicate the information. This information cannot be acquired elsewhere.”

General Matter