New Laser Technique Could Revolutionize Lithium Isotope Analysis for Fusion Energy

Recently, a team of researchers from the Korea Institute of Fusion Energy and Jeonbuk National University tested a new method for measuring lithium isotope abundance in liquid samples. This new method, which was called laser-produced vapor for laser-induced breakdown spectroscopy (LPV-LIBS), was shown to be a rapid and reliable method for this purpose (1). The findings of this study were published in Spectrochimica Acta Part B: Atomic Spectroscopy (1).

The advancement comes at a critical time for the nuclear fusion sector. Although the United States was the leader in nuclear energy for the longest time, several new countries are making inroads into this space. For example, China is investing a lot of money in this industry, ranging from $1–1.5 billion per year (2). Meanwhile, The United States is investing approximately $800 million annually (2). As part of the ongoing nuclear fusion efforts, one goal is to achieve tritium self-sufficiency in realizing a sustainable deuterium-tritium (²H–³H) fusion fuel cycle (1). Tritium, which is a rare and radioactive hydrogen isotope, can be bred from lithium-6 (⁶Li), making enriched lithium a cornerstone of future fusion reactors (1,3). However, accurate, fast, and scalable methods to analyze lithium isotope ratios are needed to ensure precise control over the fuel cycle.

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The problem is that extensive sample preparation and expensive equipment prevent traditional methods from being widely used (1). Not all laboratories and facilities have the financial resources to use these methods. Recognizing this issue, the research team designed their LPV-LIBS approach with this in mind, and they explained in their study how their approach is a simpler and faster alternative (1).

The researchers first describe the LPV-LIBS method, which combines two core laser technologies. First, a 532 nm nanosecond pulsed Nd:YAG laser beam vaporizes the liquid lithium sample (1). This process creates a vapor cloud suspended in the air within the sample container. A second laser beam, operating at 1064 nm, is then focused into the vapor cloud to produce plasma (1). The plasma emits light as lithium atoms transition between energy states, which can be analyzed to determine isotope composition (1).

Avoiding measurement pitfalls was an aspect that the researchers had to consider when building this model. To do so, they optimized the system to make the vaporization beam energy exceed 30 mJ to generate sufficient lithium vapor (1). At the same time, to suppress spectral self-reversal, which is a phenomenon that distorts measurement accuracy, the LIBS laser beam energy was capped at 30 mJ (1). Under these optimized conditions, the measured spectral shift between ⁶Li and ⁷Li was 15.7 picometers, enabling clear isotopic distinction (1).

The researchers analyzed 100 spectra over just 10 seconds, and they were able to achieve a standard error of only 2.5–5.2% in determining the ⁶Li/⁷Li ratio (1). The method was validated using liquid LiCl reference solutions with varying lithium concentrations from 0.02 mg/mL to 12 mg/mL, demonstrating that the spectral intensity increased proportionally with concentration, confirming the system’s reliability across a range of sample types (1).

As a result, the researchers demonstrated that their LPV-LIBS method can potentially be used in the fusion energy sector. Its potential for rapid and in-situ analysis could transform how to monitor and manage fuel cycles in experimental and future commercial fusion reactors (1).

One other benefit to the LPV-LIBS method is its ability to operate at atmospheric pressure. This allows researchers to not need vacuum chambers and other specialized equipment (1). This feature positions LPV-LIBS as a practical, scalable technology for fusion laboratories and potential on-site monitoring systems in lithium-processing industries (1).

The team also suggested that this method could be adapted in the future for isotopic analysis of other elements dissolved in liquids, opening the door for broad applications across environmental, pharmaceutical, and industrial sectors (1). As fusion research edges closer to practical implementation, techniques like LPV-LIBS may be able to potentially support the infrastructure required for efficient, self-sustaining reactors (1).

References

1. Tran, T. N.; Han, D.; Shim, S.; Choi, D. H. Isotopic Analysis of Liquid Lithium via Laser-produced Vapor for Laser-induced Breakdown Spectroscopy. Spectrochimica Acta Part B: At. Spectrosc. 2025, 225, 107121. DOI: 10.1016/j.sab.2025.107121
2. Dewan, A.; Nilson, E. The US led on nuclear fusion for decades. Now China is in position to win the race. CNN.com. Available at: https://www.cnn.com/2024/09/19/climate/nuclear-fusion-clean-energy-china-us (accessed 2025-05-09).
3. Government of Canada, Facts About Tritium. CNSC.gc.ca. Available at: https://www.cnsc-ccsn.gc.ca/eng/resources/fact-sheets/tritium/ (accessed 2025-05-09).