Different approaches around the world

The ITER Private Sector Fusion Workshop in May was the occasion to showcase some of the different approaches. First to take the floor during a panel on tokamaks was Alex Creely of Commonwealth Fusion Systems (CFS), a startup spun out of the Massachusetts Institute of Technology. CFS is currently building the SPARC tokamak, which is based on the same tokamak physics as ITER, but which utilizes new, high-temperature superconducting (HTS) magnets that enable much higher magnetic fields and therefore smaller tokamaks.

"In the early days of ITER, it was seen as the only viable path to a power plant," said Creely. "There are now other viable paths, however, and fusion has become a multi-polar endeavor."

CFS has already built a demonstration non-insulated toroidal field coil and tested a 20.8 Tesla HTS magnet at 20K operating temperature, storing 110 MJ of energy in 270 km of HTS tape. CFS intentionally operated this to the point of failure in order to validate its models.

Creely underscored some of the challenges ahead that the global fusion community needs to solve such as blanket and heat extraction, as well as the need for durability and reliability for commercial power plants. "ITER has the opportunity to become part of a vibrant multi-polar fusion research community, adapting to the emergence of the new private fusion industry."

He went on to stress CFS's strong support of open scientific discourse around plasma physics, and its interest in sharing physics knowledge with ITER and other fusion endeavors—both through publication and through meetings of peers. "CFS would like to see wider distribution of the documents and tools that ITER has developed. We would be very interested in gaining access to existing ITER documents and not just the planned ITER Design Handbook, which won't be published for some time. There is a lot of existing knowledge that we would be happy to benefit from right now."

The second panel participant was David Kingham from Tokamak Energy, a company founded in 2009 as a spin-off from the UK Atomic Energy Authority (UKAEA). A US subsidiary, Tokamak Energy Inc, was established in 2019, and is one of the companies selected for the US Department of Energy's bold decadal vision for fusion energy.

"Tokamak Energy is the only private fusion company with over a decade's experience developing the two technologies that offer the most efficient and commercially attractive route to fusion energy—the compact spherical tokamak and HTS magnets," said Kingham. He emphasized how HTS is a real game changer for fusion, noting that Tokamak Energy had achieved a record 24 Tesla at 20K.

He also pointed out how important the company's work on HTS magnets has been in developing technology for applications well beyond fusion. "The ability to generate intense magnetic fields in a relatively compact size makes HTS magnets attractive for applications including magnetic levitation, energy storage and lightweight, powerful electric motors and generators. Future applications could include magneto-hydrodynamic propulsion; mineral separation; proton/hadron beam therapy; particle accelerators; and space propulsion. These applications, and more, can be addressed because our magnet engineering and construction, developed for the hugely demanding requirements of fusion energy, produces magnets that are robust, compact, exceptionally powerful and easy to cool—to a typical operating temperature of 20K."

Kingham stressed the importance of ITER's body of work, citing publicly available information on the design of ITER including a grand database of tokamak experimental data, which was useful to conceptual design studies for spherical tokamaks, and advancements in tritium handling and fuel breeding systems. "ITER has also validated the performance of many important materials and stimulated the development of supply chains for materials and other enabling technologies." Kingham hopes to continue to benefit from ITER knowledge—including (good and bad) lessons learned and more detail about materials selection, and through the support of bi-directional staff secondments.

Panelist David Weisberg described research at General Atomics, which operates the DIII-D tokamak for the US Department of Energy. Whereas early tokamak designs, starting in the 1960s, were circular in cross-section, scientists at General Atomics developed the "doublet," a configuration with an elongated hourglass-shaped plasma cross-section. The Doublet I, II, and III tokamaks in the 1970s and 1980s showed that this approach allowed for a hotter and denser stable plasma. The doublet concepts evolved into the D-shaped plasmas universally seen in tokamaks today—including ITER—making General Atomics instrumental in leading this fusion research innovation.

Today, General Atomics is a major player in ITER manufacturing (central solenoid, diagnostics) but also an important player in the private-sector push forward for fusion, with specific expertise in developing and fabricating large-scale superconducting magnets for fusion applications.

"Private fusion companies are more nimble and can move more quickly than large public programs," said Weisberg, "but we do so at increased programmatic risk. We believe that ITER can play an important role in reducing risk for the private sector by becoming the knowledge base for tomorrow's fusion industry. For example, General Atomics is focusing on reducing risk through technology development that is informed by integrated facility design studies. ITER is already a world leader in this approach, and so we believe there is an important opportunity for ITER to disseminate this knowledge, both through the ITER Design Handbook as well as through person-to-person education."

Calling the design and construction of ITER "singular accomplishments that have generated a wealth of knowledge," he said that ITER is closing fusion technology gaps and raising technology readiness levels. ITER "has already solved many of the integration challenges that a fusion pilot plant will face" but he believes ITER can do more. "The people behind the ITER design decisions are the most valuable resource for the private sector. The ITER Organization could expand its education efforts to include seminars, workshops, and summer schools for future fusion developers. And it could host industry partners on site to facilitate knowledge transfer, because in-person collaboration is the best way to pass on programmatic and development skills."

Minsheng Liu from China's ENN Energy Research Institute agrees. "Good examples of how ITER can help include knowledge-sharing, such as the theory and modelling resources delivered by the ITER integrated modelling and analysis suite (IMAS), and the co-development of key technologies, such as negative-ion based neutral beam injector (N-NBI) technology."

Between 2018 and 2022, Liu's group designed and built EXL-50, China's first medium-sized spherical torus experimental device, which established the basis of spherical tokamak proton-boron fusion. In 2022, ENN began to upgrade to EXL-50U and design a new device, EHL-2—a spherical torus R&D platform to tackle key proton-boron fusion challenges including the much higher temperatures needed. The next step—Phase II—will be EHL-3A & 3B, which aim to improve parameters and overcome the engineering constraints for scaling up to a fusion reactor. Phase III will be the engineering and commercial demo, which will also focus on reducing costs.

Liu joined the other speakers in emphasizing the importance of cooperation and collaboration in the fusion community and the value of learning by doing, drawing from expertise in fusion, high-energy particles, laser and materials. He said that ENN prioritized engaging experts from universities, laboratories, industries, power companies and private enterprises.

Liu also highlighted the importance of digital intelligence in fusion research. "Through intelligent simulation design, operation control, and experimental analysis of the spherical torus device—integrating physics, diagnosis, and control—we can help to expedite device design, enhance device design reliability, accelerate analysis and the comprehension of experimental results, and accomplish intelligent device control. We can digitize actual experiments and perform them on the computer. Our virtual, intelligent spherical torus experimental platform is flexible, capable of intelligent evolution, and able to extrapolate and predict without being constrained by current engineering technologies."

During the Q&A session following the presentations, all four speakers agreed that one of the key problems facing the industry is the shortage of engineers, suggesting that more funding for training was needed both in universities and public companies.

"But students won't get involved if the industry doesn't exist, if the finish line isn't in sight," said Weisberg. "So we really need to bootstrap and to make this happen."

And that, surely, is another way ITER can help.