A team at the Massachusetts Institute of Technology (MIT) created the highest plasma pressure ever recorded, using its Alcator C-Mod tokamak reactor. High pressures and extreme temperatures are vital in forcing atoms together to release huge amounts of energy.
Nuclear fusion powers the sun and has long been touted as the ultimate solution to powering the world while halting climate change. But, as fusion sceptics often say, the reality has stubbornly remained a decade or two away for many years.
Now MIT scientists have increased the record plasma pressure to more than two atmospheres, a 16% increase on the previous record set in 2005, at a temperature of 35 million C and lasting for two seconds. The breakthrough was presented at the International Atomic Energy Agency’s fusion summit in Japan on Monday.
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Successful fusion means getting more energy out than is put in and this requires the combination of pressure, temperature and time to pass a critical value at which point the reaction becomes self-sustaining. This remains elusive but the MIT record shows that using very high magnetic fields to contain the plasma may be the most promising route to practical nuclear fusion reactors.
Power plant prototype
The new reactor is designed for basic research on fusion and also as a potential prototype power plant that could produce significant power. The basic reactor concept and its associated elements are based on well-tested and proven principles developed over decades of research at MIT and around the world, the team says.
“The much higher magnetic field,” Sorbom says, “allows you to achieve much higher performance.”
Tenfold boost in power
While the new superconductors do not produce quite a doubling of the field strength, they are strong enough to increase fusion power by about a factor of 10 compared to standard superconducting technology, Sorbom says. This dramatic improvement leads to a cascade of potential improvements in reactor design
Another key advantage is that most of the solid blanket materials used to surround the fusion chamber in such reactors are replaced by a liquid material that can easily be circulated and replaced, eliminating the need for costly replacement procedures as the materials degrade over time.
The giant, seven-storey-high tokamak is being built in southern France, with magnets weighing about the same as a Boeing 747. The volume of ITER’s tokamak will be 800 times bigger than the MIT vessel. ITER should be completed in 15-20 years and aims to deliver 500MW of power, about the same as today’s large fission reactors. But the project has been hampered by delays.
“This is a remarkable achievement,” said Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory. “The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy.”