The Korean artificial sun, KSTAR, has completed diverter upgrades, allowing it to operate and sustain high-temperature plasma over 100 million degrees for extended periods.
The Korea Institute of Fusion Energy announced the successful installation of the newly developed tungsten diverter for KSTAR. KSTAR, now equipped with the new diverter, commenced a plasma experiment on the 21st of December, 2023.
The diverter, a crucial plasma-facing component installed at the bottom of the vacuum vessel in a magnetic fusion device known as a Tokamak, manages the exhaust of waste gas and impurities from the reactor and also endures the highest surface heat loads. This is why it is important to develop and deploy a highly heat-resistant diverter.
Initially, KSTAR had a carbon diverter, but for KSTAR’s enhanced performance and prolonged operations at 100 million ℃, the heat flux exceeded the limit of the carbon diverter.
Consequently, the development of a diverter using tungsten began in 2018. The first prototype was completed in 2021, and a new diverter was installed in September 2022 for approximately one year. The recently installed diverter comprises 64 cassettes, each crafted from tungsten mono-blocks. These 64 cassettes fully surround the bottom of the vacuum vessel.
Tungsten material possesses a high melting point and low sputtering characteristics. Therefore, the heat flux limit has improved by over two-fold compared to the carbon diverter, reaching 10 MW/m².
The plasma experiments of KSTAR in the new tungsten diverter environment will continue until February 2024. The primary objectives include verifying stable operations in the new tungsten diverter environment and reproducing KSTAR’s 100-million-degree plasma.
KFE President Dr. Suk Jae Yoo stated, “In KSTAR, we have implemented a divertor with tungsten material, which is also the choice made in ITER. We will strive to contribute our best efforts in obtaining the necessary data for ITER through KSTAR experiments.”
Previously, KSTAR has demonstrated high-performance plasma operation for 30 seconds with ion temperatures over 100 million degrees, and now the goal is to achieve 300 seconds by the end of 2026 with this new diverter.
