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MIT reactor sets nuclear fusion record on the day it's closed down

Lucas Mearian | Oct. 19, 2016
Funding for an international fusion reactor signaled the end of MIT’s project

A fusion reactor at MIT that has repeatedly set world records over its 23-year lifespan broke one more the day before it was shuttered due to defunding by the federal government.

MIT's Plasma Science and Fusion Center (PSFC) announced it achieved 2.05 atmospheres of pressure in its tokamak-type (doughnut-shaped) nuclear fusion device -- the Alcator C-Mod, or ARC. Pressure, which contains and concentrates superheated plasma, is key to creating a fusion device that is self-sustaining.

alcator c mod fusion reactor 
A look at the exterior of MIT's C-Mod nuclear fusion device. The C-Mod project paved the way for a conceptual ARC prototype reactor.

With this result, the Alcator C-Mod broke its own record of 1.77 atmospheres, which was set in 2005.

"This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at MIT," Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory, who was not directly involved in the experiments, told MIT News. "The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy."

What MIT alone has done is create the world's strongest magnetic containment field for a reactor of its size. The higher the magnetic field, the greater the fusion reaction and the greater the power that's produced.

MIT's fusion reactor is the smallest tokamak-type device. Computerworld toured the facility and spoke with PSFC Director Dennis Whyte, who explained how the experiments were paving a "viable pathway forward" in plasma containment to make net fusion energy.

The C-Mod's high-intensity magnetic field — up to 8 Tesla, or 160,000 times the Earth's magnetic field — allows the device to create the dense, hot plasmas and keep them stable at more than 80 million degrees, according to MIT. Its magnetic field is more than double what is typically used in other designs, which quadruples its ability to contain the plasma pressure.

The goal of the Alcator C-Mod, also known as ARC (for affordable, robust, compact reactor), was to pave the way toward producing the world's smallest fusion reactor -- one that crushes a doughnut-shaped fusion reaction into a 3.3-meter radius -- three of which could power a city the size of Boston.

Making a smaller reactor would also have made it less expensive to build. Additionally, the ARC would be modular, allowing its many parts to be removed for repairs to upgrades, a step not previously achieved.

Currently, the main hurdle to fusion energy is sustainability. The fusion reaction is only momentary and requires more energy to create than it generates.

While three other fusion devices roughly the same size as the ARC have been built over the past 35 years, they didn't produce anywhere near its power. What set MIT's reactor apart was its superconductor technology, which would enable it to create 50 times the power it actually draws.


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