A researcher from MEPhI determined the optimal conditions for working with lithium as the material of the inner walls of a tokamak (a device for confining plasma in a magnetic field - the main part of a hypothetical thermonuclear reactor). Thus, another important step towards the creation of "thermonuclear reactors with magnetic plasma confinement" has been made. The research results were published in the Journal of Nuclear Materials .

One of the key unresolved issues in the creation of a fusion tokamak reactor is the choice of material for coating the elements of the inner wall of the reactor, which should be in contact with the plasma. Liquid lithium can become such a material.

“The use of liquid lithium helps to avoid problems with local damage accumulation and gives the cell surface the ability to self-heal. However, when used as a material in contact with plasma, liquid lithium will evaporate, and it will be necessary to create special collectors that collect its particles,” says Stepan Krat, Ph.D. Senior Researcher of the Laboratory of Physicochemical Processes in the Walls of Thermonuclear Installations and the Department of Plasma Physics of the Institute for Laser and Plasma Technologies (LaPlas) of the MEPhI.

 The scientist noted that during the deposition of lithium, hydrogen can accumulate in its layers, which can lead to the precipitation of solid hydride precipitation. These substances can adversely affect the operation of circuits designed to use liquid lithium. The efficiency of lithium collection by the collector, the amount of accumulated hydrogen in the layer deposited from the plasma, and the phase composition of the layer depend on the deposition conditions and require detailed study, he added.

To establish the optimal operating conditions for the lithium coating, experiments were carried out at MEPhI on laboratory benches.

“We have found that the amount of deuterium in a co-deposited lithium-deuterium layer can be as high as 30 atomic percent. At the same time, most of the deuterium is contained in the form of a hydride in the layer, which decomposes in vacuum when heated to a temperature of 700 K. Part of the deuterium is released at higher temperatures, probably in the process of decomposition of complex lithium-deuterium-nitrogen compounds,” said Stepan Krat.

According to him, the temperature range of 250-300°C will be the most efficient thermal regime for future collectors in tokamaks with lithium cells.

“Under these conditions, the efficiency of lithium collection from plasma is still high, and the deuterium content in the layer drops sharply,” the scientist added.