Scientists fire up nuclear fusion experiment

After "decades of quiet progress" international scientists have taken a major step in their quest to harness nuclear fusion to generate cheap and clean electricity.

Seven countries have signed an agreement in Brussels to launch the largest fusion-energy experiment ever conducted.

The collaboration paves the way for the construction of a multibillion dollar International Thermonuclear Experimental Reactor (ITER) in southern France.

The US, China, the European Union, India, Japan, the Republic of Korea and the Russian Federation are joint sponsors of the project, which will experimentally generate up to 500 million watts of energy.

An international collective of physicists and engineers is working to complement and lend expertise to the ITER initiative, and researchers at the University of Wisconsin-Madison are firmly placed among them.

"[ITER] is a major threshold that we've been waiting to get to for 20 years, " said Raymond Fonck, a University of Wisconsin-Madison professor of engineering physics and the chief scientist of ITER's US project office.

"The project is the number one priority in fusion research in the country and the world, and essentially takes us to a regime we've never been to before."

Fusion energy is released when atomic particles "fuse" together to form heavier particles. Physicists have tried to harness the energy potential of nuclear fusion by working with plasma particles, such as hydrogen nuclei, that carry electric charge.

Because hydrogen can be easily extracted from seawater - a cheap and abundant resource - scientists have been tantalised by the prospect of plasma one day serving as an inexhaustible fuel.

But plasma has to be very hot - of the order of millions of degrees - for its gas particles to efficiently collide and release energy.

"Basically, we're trying to make a sun here on Earth," said Stewart Prager, a University of Wisconsin-Madison physics professor, who also advises the US government on national fusion-energy research. "But it turns out to be one of the most difficult scientific problems in the world."

One of the biggest hurdles is finding a container that can hold searing hot plasma without burning down itself.

Scientists have been working around the problem by using magnetic fields to hold the plasma in place, but they are still searching for the most efficient and optimal ways to do it.