In the heart of China’s fusion energy research, a team led by Yuming Liu from the Institute of Plasma Physics at the Chinese Academy of Sciences has made significant strides in understanding boron’s role in plasma-facing components (PFCs). Their work, recently published in the English-language journal Nuclear Fusion, could have profound implications for the future of nuclear fusion reactors, particularly for the International Thermonuclear Experimental Reactor (ITER).
Boronization, a technique used to coat the inner walls of fusion reactors, is crucial for suppressing impurities and getting oxygen. Liu’s team conducted extensive experiments on the Experimental Advanced Superconducting Tokamak (EAST) to assess boron’s performance under metal wall conditions. Using a quartz crystal microbalance (QMB) positioned in a magnetic shadowed area, they monitored material erosion and deposition during wall conditioning and plasma discharges.
The findings were striking. “We observed material erosion in over 50% of discharges, whether normal operations or disruptions,” Liu explained. The team discovered that erosion rates were significantly influenced by the heating configuration, with electron cyclotron resonance heating (ECRH) discharges inducing erosion rates nearly twice as high as combined lower hybrid wave and ECRH discharges.
One of the most compelling insights was the transition from erosion to deposition during normal discharges. This transition provides critical data for estimating the lifetime of boron-based coatings on nearby PFCs. Following a single boronization using 10 grams of carborane, the boron-based coating on the QMB exhibited a lifetime of approximately 10,000 seconds under plasma exposure.
Post-mortem analyses revealed a residual boron-carbon film about 30 nanometers thick, demonstrating strong oxygen gettering capability and minor iron and copper contamination. This film exhibited a deuterium retention level more than eight times higher than that of pure tungsten, highlighting the pronounced trapping capacity of boron-containing films in low-flux regions.
The implications for the energy sector are substantial. As ITER and other next-step fusion devices move closer to reality, understanding the behavior of boron in these extreme environments becomes increasingly important. Liu’s research provides valuable insights into the application of boron, potentially extending the lifespan of PFCs and improving the overall efficiency of fusion reactors.
“This research not only advances our scientific understanding but also paves the way for practical applications in future fusion energy devices,” Liu noted. The findings could influence the design and maintenance strategies for ITER and other advanced fusion reactors, ultimately contributing to the commercial viability of fusion energy.
As the world looks towards cleaner and more sustainable energy sources, Liu’s work offers a glimpse into the future of fusion energy, where boron could play a pivotal role in achieving stable and efficient plasma conditions. The journey towards commercial fusion energy is long and complex, but with each breakthrough, the path becomes clearer and more attainable.