MIT researchers and a university startup announced a key milestone for bringing a demonstration fusion plant online in 2025.
The successful testing of a high-temperature superconducting magnet was reported by startup Commonwealth Fusion Systems (CFS) and MIT’s Plasma Science and Fusion Center. MIT researchers and CFS said the 20-tesla field strength is the most intense magnetic field ever generated on Earth, opening a path to construction of the first fusion power plant.
Among the most significant challenges for creating conditions necessary for fusion is magnet design. The researchers reported it is now feasible to build and confine plasma that produces more energy than it consumes using magnet technology developed by the MIT-CFS team.
“This unique partnership and collaboration between MIT and CFS allowed us to be nimble and fast in designing, building and testing this magnet,” Dennis Whyte, director of MIT’s Plasma Science and Fusion Center, said a press briefing. “We were able to draw from and build on the strengths of each organization and create a team to deliver this technology on the rapid timescale demanded by the climate crisis.”
The hurdles of fusion are undeniably high. If demonstrated, MIT’s technology may become a carbon-free, limitless source of energy. The demonstration also represents a significant step toward addressing the most pressing issues regarding an MIT initiative called SPARC, a high-field fusion energy experiment. SPARC is intended to attain a fusion gain, or Q-factor, of at least 2, implying that twice as much fusion energy is generated as the amount of used to sustain a reaction. A demonstration device is scheduled to be completed in 2025.
“The goal here is basically a power plant the size of a small high school gym, that produces as much power as a coal plant with zero carbon. And the fuel is hydrogen, that comes from water, which we have an inexhaustible supply of,” said Maria Zuper, vice president of MIT Research.
Fusion is the process that powers the Sun. In a fusion reaction, two light nuclei merge to form a single heavier nucleus, releasing energy since the total mass of the resulting single nucleus is less than the mass of the two original nuclei. The leftover mass becomes energy.
A magnetic field retains the collection of protons and electrons, or plasma, creating an unseen cloak. Magnetic fields exert a significant control on electrically-charged particles. A doughnut-shaped structure known as a tokamak is the most popular design for containment. More than 150 tokamaks have been created and operated, each demonstrating functionality by approaching the fusion point. While most devices utilize copper electromagnets to generate magnetic fields, the French ITER design employs so-called low-temperature superconductors.
A key advance in the MIT-CFS fusion effort, according to the researchers, is the use of high-temperature superconductors that allow for a considerably stronger magnetic field and resulting smaller tokamaks. That was achieved using a new superconducting material, a rare-earth barium copper oxide (ReBCO) operating at 20 degrees Kelvin. A ribbon-shaped version of ReBCO only became commercially accessible several years ago. The application of new high-temperature superconducting magnets leveraged decades of experimental results gained from tokamak experiments.
Magnet development required three years of design along with supply chain and production process development. Researchers said numerous prototypes was generated using a physical model and CAD designs.
The new magnet was gradually charged in a series of steps until it attained a magnetic field of 20 tesla. That represents “the greatest field strength yet achieved by a high-temperature superconducting fusion magnet,” the fusion researchers claimed. The magnet consists of 16 plates stacked on top of each other. In order to create a strong magnetic field, researchers said the material must be contained in a strong metal structure.
The scale and performance of the new magnet is similar to a non-superconductor magnet used in a MIT’s Alcator C-Mod experiment completed in 2016. “The difference in terms of power consumption is rather stunning,” Whyte said, “because it was a normal copper conducting magnet [consuming] approximately 200 million watts of energy to produce the confining magnetic field.”
The new magnet used about 30 watts, Whyte said, meaning the amount energy needed to confine the magnetic field was reduced by a factor of about 10 million. The switch to a high-field superconducting device could lead to “net energy from fusion [because] we don’t have to use so much power to provide the confining magnetic field,” he aded.
The MIT fusion center test also revealed that a scale-built magnet could maintain a field of more than 20 tesla, the performance level required for the SPARC tokamak device that will be used to demonstrate net energy from fusion.
That test involves achieving temperatures sufficient for a superconducting magnet to create a field while limiting power consumption. The magnitude of the field strength, which took several days to ramp up, was deemed sufficient to maintain what designers considered a steady state in which balance was achieved between energy consumption and temperature.
The next step is constructing SPARC, using the successful magnet test as a foundation. Significant technical and economic challenges remain, but researchers believe the road to fusion energy may finally be running downhill.
This article was originally published on EE Times.
Maurizio Di Paolo Emilio holds a Ph.D. in Physics and is a telecommunication engineer and journalist. He has worked on various international projects in the field of gravitational wave research. He collaborates with research institutions to design data acquisition and control systems for space applications. He is the author of several books published by Springer, as well as numerous scientific and technical publications on electronics design.