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Scientists use plasma shaping to control turbulence in stellarators
Researchers at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) and the Max Planck Institute of Plasma Physics in Germany have devised a new method for minimizing turbulence in bumpy donut-shaped experimental fusion facilities called stellarators. This month in a paper published in Physical Review Letters, these authors describe an advanced application of the method that could help physicists overcome a major barrier to the production of fusion energy in such devices, and could also apply to their more widely used symmetrical donut-shaped cousins called tokamaks. This work was supported by the DOE Office of Science.
Turbulence allows the hot, charged plasma gas that fuels fusion reactions to escape from the magnetic fields that confine the gas in stellarators and tokamaks. This turbulent transport occurs at comparable levels in both devices, and has long been recognized as a challenge for both in producing fusion power economically.
"Confinement bears directly on the cost of fusion energy," said physicist Harry Mynick, a PPPL coauthor of the paper, "and we're finding how to reshape the plasma to enhance confinement."
The new method uses two types of advanced computer codes that have only recently become available. The authors modified these codes to address turbulent transport, evolving the starting design of a fusion device into one with reduced levels of turbulence. The current paper applies the new method to the Wendelstein 7-X stellarator, soon to be the world's largest when construction is completed in Greifswald, Germany.
Results of the new method, which has also been successfully applied to the design of smaller stellarators and tokamaks, suggest how reshaping the plasma in a fusion device could produce much better confinement. Equivalently, improved plasma shaping could produce comparable confinement with reduced magnetic field strength or reduced facility size, with corresponding reductions in the cost of construction and operation.
At the Korea Institute of Fusion Energy (KFE), the KSTAR tokamak recommenced operations in December after a major upgrade to replace the…
KSTAR aims for longer plasmas
At the Korea Institute of Fusion Energy (KFE), the KSTAR tokamak recommenced operations in December after a major upgrade to replace the device's carbon divertor with a tungsten divertor.
According to an article on the KFE website, the original carbon divertors could take a thermal load of 5MW/m², whereas the tungsten divertor can take 10MW/m². The upgrade is critical to the goal of sustaining a 100-million-degree plasma for 300 seconds by 2026. Data from the operational campaign will be directly relevant to ITER, which will operate a tungsten divertor under similar plasma conditions in terms of shape and structure.
This testing campaign will continue through February 2024. Read more about the plans in this article in English on the KFE website, or in Korean in the Chosun Biz.