The Korea Superconducting Tokamak Advanced Research (KSTAR) at the Korea Institute of Fusion Energy (KFE) in Daejeon has broken its previous plasma operation record, achieved during its first plasma campaign, following the upgrade of its divertors (plasma facing components) to tungsten monoblocks. KFE said it had sustained the plasma with ion temperatures of 100 million degC for 48 seconds during the KSTAR plasma campaign run from December 2023 to February 2024. Additionally, it achieved the high confinement mode (‘H-mode’) for over 100 seconds.

KSTAR achieved its milestone of reaching 100 m degC plasma in 2018 for the first time, and set a new record by sustaining plasma with an ion temperature of 100 m degC for 30 seconds in 2021. This latest achievement was founded on improvements in the performance of the plasma heating systems and advancements in high-temperature plasma operation and control techniques.

KSTAR also successfully maintained H-mode for a continuous duration of 102 seconds. H-mode is the baseline operation mode for sustaining a high-temperature, high-density plasma state.

Improved divertors

These improvements are mainly due to the upgrade applied to KSTAR’s divertors with tungsten in 2023. Compared with the previous components based on carbon, the new tungsten divertors showed only a 25% increase in surface temperature under similar heat loads. This provides significant advantages for long-pulse high heating power operations. The experiments proved that the tungsten divertors were functioning as planned. They also confirmed that key components of KSTAR, such as heating, diagnostics and control systems, had ensured the system reliability required for prolonged plasma operations.

Dr Si-Woo Yoon, director of the KSTAR Research Centre commented: “To achieve the ultimate goal of KSTAR operation, we plan to sequentially enhance the performance of heating and current drive devices and also secure the core technologies required for long-pulse high performance plasma operations.”

The ultimate goal of KSTAR is to achieve 300 seconds of plasma operation with ion temperatures over 100 m degC.

Research at KSTAR is used to support development of the International Thermonuclear Experimental Reactor (ITER) under construction in Cadarache, France and DEMO, the demonstration fusion power plant currently under design by the European fusion community. KFE president Dr Suk Jae Yoo said the latest research is “a green light for acquiring core technologies required for the fusion DEMO reactor”. He added: “We will do our best to secure core technologies essential for the operation of ITER and the construction of future DEMO reactors.”

Image: The Korea Superconducting Tokamak Advanced Research (KSTAR) at the Korea Institute of Fusion Energy (courtesy of KFE)