In a significant stride toward sustainable fusion energy, researchers at the Experimental Advanced Superconducting Tokamak (EAST) in China have developed a novel technique to extend the duration of high-performance plasma discharges, a critical milestone for future fusion reactors. The findings, published in the journal *Nuclear Fusion* (which translates to *Fusion* in English), offer promising insights into managing fuel recycling and impurity control, key challenges in the quest for practical fusion power.
The study, led by Dr. Zhen Wang from the Institute of Plasma Physics at the Chinese Academy of Sciences and the University of Science and Technology of China, focuses on the behavior of fuel recycling and impurity accumulation during long-pulse H-mode plasmas under full metal wall conditions. H-mode, or high-confinement mode, is a state of operation in a tokamak where the plasma’s energy confinement time is significantly improved, a crucial factor for achieving net energy gain.
“Significant fuel recycling and impurity rising, particularly from heavy impurities, have been observed when operating with a bare metal wall or a deteriorate real-time coated wall,” Dr. Wang explained. “This severely limits the duration of H-mode discharges.” To tackle this issue, the team developed a dynamic wall coating technique that combines feedforward and feedback controls. The feedforward control presets the lithium (Li) powder injection rate based on prior experimental observations, while the feedback control dynamically modulates the Li injection rate in response to real-time Li-II line emission measurements.
This innovative approach enabled the team to achieve a remarkable 605-second H-mode plasma discharge, extending the previous record of 403 seconds by over 200 seconds. “Using this approach, we have successfully maintained stable fuel recycling and impurity levels, demonstrating the effectiveness of the dynamic powder injection technique,” Dr. Wang stated.
The implications of this research are substantial for the energy sector. Efficient fuel recycling and impurity control are vital for the commercial viability of fusion power. By extending the duration of high-performance plasma discharges, this technique brings us closer to the realization of sustainable, large-scale fusion energy. Moreover, the findings suggest potential applications for other low-Z powders, such as boron, in international fusion projects like ITER.
As Dr. Wang noted, “These results offer valuable insights into potential applications of other low-Z powder in ITER, paving the way for future developments in the field.” The dynamic powder injection technique developed by Dr. Wang and his team represents a significant step forward in our understanding of plasma-wall interactions, a critical area of research for the future of fusion energy. With continued advancements in this field, the dream of clean, abundant, and sustainable fusion power may soon become a reality.