1,337 seconds or more than 22 minutes: that was how long WEST, a tokamak run from the CEA Cadarache site in southern France and one of the EUROfusion consortium medium size Tokamak facilities, was able to maintain a plasma for on 12 February. This was a 25% improvement on the previous record time achieved with EAST, in China, a few weeks previously.
Reaching durations such as these is a crucial milestone for machines like ITER, which will need to maintain fusion plasmas for several minutes. The end goal is to control the plasma, which is naturally unstable, while ensuring that all plasma-facing components are able to withstand its radiation without malfunctioning or polluting it.
“I would like to congratulate the WEST team and collaborators for yet another important achievement. WEST is an important facility for preparing the ITER exploitation towards the development of fusion energy. WEST plays an important role in implementing the EUROfusion programme within EURATOM, as one of the key Tokamaks facilities in Europe.”
adds Gianfranco Federici – EUROfusion Programme Manager.
This is what CEA researchers intend to achieve and what explains the current record. Over the coming months, the WEST team will double down on its efforts to achieve very long plasma durations – up to several hours combined – but also to heat the plasma to even higher temperatures with a view to approaching the conditions expected in fusion plasmas.
For these long-duration plasmas, scientists from CEA-IRFM use one of the plasma heating antennas using lower hybrid radiofrequency waves, called LH antennas. In the record plasma, a heating power of 2 MW is injected by a single antenna. It generates a current in the plasma by accelerating electrons and thus stabilizes it. On Wednesday, February 12, a first hydrogen plasma with a duration of 819 seconds was achieved, demonstrating the robustness of the previously used scenario. The following plasma, number 61299, was sustained for 1337 seconds, or 22 minutes, with a power injected by the LH system and extracted by the actively cooled tungsten components facing the plasma of 2.6 GJ.
The WEST experimental program continues with the objective of increasing the plasma heating power to, on the one hand, transition into the improved confinement mode envisaged for ITER in its DT phase, which will require adapting the plasma control schemes, and on the other hand, to increase the power on the components facing the plasma and simulate higher fusion powers. The ambition is to increase the heating power from 2 MW to 10 MW, still over durations of the order of 1000 seconds, a power that corresponds to a fusion power of the order of GW in a machine the size of ITER. This will allow the evaluation of the lifetime of the tungsten components facing the plasma in these extreme conditions.
Mastering this inherently unstable plasma over long durations is a true technological challenge and an essential prerequisite for controlling a self-sustained plasma driven by fusion reactions, as will be the case in ITER, and ultimately for producing fusion energy on an industrial scale.
