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US reactor breaks fusion record – then runs out of cash and shuts down

MIT hardware under pressure

Video In a tale that tells you all you need to know about the parlous state of American science, a fusion reactor has broken plasma-handling records in the last few days before losing its funding.

The Alcator C-Mod tokamak nuclear fusion reactor, run for the past 23 years by MIT's Plasma Science and Fusion Center, managed to contain 35 million degrees Celsius plasma at a pressure of 2.05 atmospheres, beating the previous world record by over 15 per cent.

"This is a remarkable achievement that highlights the highly successful Alcator C-Mod program at MIT," said Dale Meade, former deputy director at the Princeton Plasma Physics Laboratory, who was not directly involved in the experiments.

"The record plasma pressure validates the high-magnetic-field approach as an attractive path to practical fusion energy."

In order to get fusion reactions to work, plasma must be heated to millions of degrees Celsius and its density must be highly controlled by pressure. The MIT reactor used 1.4 million amps of electrical current and a magnetic field strength of 5.7 tesla to contain the plasma in a one-cubic-meter volume and sustained 600 trillion fusion reactions over two seconds.

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"This result confirms that the high pressures required for burning plasma can be best achieved with high-magnetic-field tokamaks such as Alcator C-Mod," said Riccardo Betti, the Robert L McCrory Professor of Mechanical Engineering and of Physics and Astronomy at the University of Rochester.

The results, announced on Monday at the International Atomic Energy Agency Fusion Energy Conference in Japan, are cause for celebration – but a bittersweet one, since the reactor is now being decommissioned due to lack of funds. Instead, the US and several other nations are ploughing their funding into the much-delayed International Thermonuclear Experimental Reactor (ITER) project.

ITER, currently under construction in southern France, is supposed to be the most advanced fusion reactor the world has ever seen, designed from the ground up to incorporate the best research in an entirely custom-built facility capable of producing 500MW of power.

But the project has run into massive cost overruns. Originally estimated to cost $5bn, the facility will now cost over $15bn and won't be operational until the next decade. The EU isn't happy about this, nor are other partners, since it means funds have to be diverted from other fusion projects to make up the shortfall.

Because of this delay, MIT's plasma pressure record is likely to last for a long time – possibly as long as a decade, thanks to having very little competition. Nevertheless, commercial fusion remains – as it has for the last few decades – about 120 years away, promise. ®

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