In the relentless pursuit of harnessing fusion energy, scientists have long grappled with a critical challenge: understanding and monitoring helium retention in the materials that face the brutal environment of fusion plasmas. A recent breakthrough, published in the journal *Nuclear Fusion* (translated as *Fusion Nuclei*), offers a promising solution that could significantly advance the field.
Researchers, led by Zhonglin He of the Key Laboratory of Materials Modification by Laser, Ion and Electron Beams at Dalian University of Technology, have developed a novel approach to detect helium in high-Z materials like tungsten and molybdenum. Their method combines laser-induced breakdown spectroscopy (LIBS) with laser-induced desorption quadrupole mass spectrometry (LID-QMS), achieving unprecedented sensitivity.
“Helium retention is a crucial factor in plasma-wall interactions,” He explains. “By optimizing the LIBS technique under vacuum conditions, we’ve been able to significantly improve the signal-to-noise ratio and achieve the lowest detection limits reported to date for high-Z materials.”
The team identified the He I 587.56 nm spectral line as the optimal signal for LIBS, resilient to interference from high-Z elements. By fine-tuning the gate delay timing and leveraging spatial plasma emission characteristics, they excluded core plasma emissions where background noise and matrix interference are most intense. This optimization led to a threefold improvement in the signal-to-noise ratio.
To ensure accuracy, the researchers used LID-QMS as a reference to establish quantitative calibration curves. Internal standardization reduced prediction errors to an impressive 10% or less, even with variable laser ablation rates. The limits of detection achieved for helium in molybdenum and tungsten co-deposited layers are 0.72 × 10^14 He mm^−2 (0.09 at.%) and 0.84 × 10^14 He mm^−2 (0.11 at.%), respectively.
This breakthrough could have significant implications for the energy sector, particularly in the development of fusion power plants. Accurate, real-time monitoring of helium retention is essential for understanding plasma-wall interactions and designing more robust plasma-facing components.
“The practical applications of this research are vast,” He notes. “Our approach paves the way for in situ diagnostics in tokamaks like ITER and EAST, enabling precise characterization of plasma-wall interactions and facilitating advancements in plasma-facing component design.”
As the world looks to fusion energy as a potential solution to its energy needs, innovations like this one bring us one step closer to making fusion a reality. By providing a robust methodology for in situ helium retention monitoring, this research not only addresses a longstanding challenge but also opens new avenues for exploration and development in the field of fusion energy.