Lithium promotes hot plasma edge for fusion

Article by Adam Duckett

LITHIUM could hold the key to improving the confinement of plasma in fusion reactors, and ensuring the walls of the device survive bombardment by energetic particles.

Experiments at the Lithium Tokamak Experiment (LTX) facility at Princeton University in the US have showed that coating the walls with solid lithium produces temperatures that stay constant from the hot plasma core through to its outer edge, the research team reports in Physical Review Letters.

This is important because the edge of the plasma, just a few meters from the 100m oC core, would normally be a much cooler few thousands degrees. This is because stray plasma particles recycle cold gas from the walls of the tokamak reactor back into the edge of the plasma. But the lithium coating prevents this.

"This is the first time that anybody has shown experimentally that the edge of the plasma can remain hot due to reduced recycling," said lead research author Dennis Boyle.

A hotter edge would improve operational efficiency by reducing the amount of heating required to keep the plasma hot enough for fusion to occur.

The team says that using flowing liquid lithium could improve on the solid coatings by absorbing hot particles without degrading, so reducing damage to the tokamak walls.

The team is now upgrading the experimental reactor to operate at higher temperatures and test whether lithium can keep the plasma temperature constant in these conditions.

Efforts to develop nuclear fusion power are being undertaken around the world, including at the Joint European Torus (JET) facility in the UK, and the Iter facility in France, which is set to be the largest tokamak when it comes online in the 2020s. If fusion power proves possible, it promises a clean, almost inexhaustible, source of energy.

Physical Review Letters:  

Article by Adam Duckett

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