A multinational team says it’s finally explained how the behavior of plasma – the extremely hot gases of nuclear fusion – can be controlled using ultra-thin lithium films on graphite walls lining thermonuclear magnetic fusion devices.
To answer the question, they combined predictions from quantum-mechanical supercomputer simulations on the Kraken and Jaguar systems at Oak Ridge National Laboratory and in situ experimental results from the Purdue group.
“Surprisingly, we find that the presence of oxygen in the surface plays the key role in the bonding of deuterium, while lithium’s main role is to bring the oxygen to the surface,” says Predrag S. Krstic of the Joint Institute for Computational Sciences
“Deuterium atoms preferentially bind with oxygen and carbon-oxygen when there is a comparable amount of oxygen to lithium at the surface. That finding well matches a number of controversial experimental results obtained within the last decade.”
One of the biggest practical problems for thermonuclear magnetic fusion has been understanding what takes place at the interface where the plasma and boundary fusion reactor walls meet.
The study of the lithium coatings also impacts many areas beyond magnetic fusion, says the team, including nanoelectronics, lithium batteries, computational materials science, bioengineering and biophysics, plasma physics, and theoretical physics and chemistry.
“This work can lead to improvement of the hydrogen-recycling properties of the fusion materials facing plasma, as well as advancements in other areas,” says Krstic.
“We hope that our finding will inspire future theoretical and experimental work in diverse applications not only with lithium coatings on various materials but also with combinations of other types of materials that are potentially good ‘oxygen-getters’ – for example elements of the first two groups of the periodic system.”
