A Forgotten Jewelers' Secret May Power Future Nuclear Clocks

A Breakthrough in Nuclear Clock Technology

In 2008, a team of scientists from the University of California, Los Angeles (UCLA) proposed a groundbreaking idea: using a laser to excite the nucleus of thorium atoms to create highly accurate, portable clocks. Last year, they successfully realized this vision by bombarding thorium atoms embedded in specialized fluoride crystals with a laser. Now, they have taken another significant step forward by simplifying and strengthening the process through a novel approach that involves electroplating thorium onto steel.

This advancement has the potential to revolutionize timekeeping technology, making nuclear clocks more compact, efficient, and accessible. These improvements could have far-reaching implications for navigation, GPS systems, power grids, and communications. Additionally, they may enable some of the most precise tests of fundamental physics ever conducted.

A New Method Using Thorium on Steel

Previously, the UCLA-led team used specialized fluoride crystals to stabilize thorium-229 nuclei while allowing laser light to excite them. However, this method was complex, required large amounts of thorium, and was difficult to scale. The latest development replaces these crystals with a thin layer of thorium electroplated onto steel, significantly reducing the amount of thorium needed and making the process more robust.

The key to this breakthrough was realizing that a long-held assumption was incorrect. Scientists had believed that the material containing the thorium needed to be transparent to allow the laser light to reach the nucleus. However, the new method demonstrates that even opaque materials can be used, as the excited nuclei emit electrons instead of photons. This allows researchers to detect the nuclear transition simply by monitoring an electrical current, which is much easier than detecting light emissions.

Overcoming Challenges and Simplifying the Process

The journey to this point has been long and challenging. Hudson's group spent 15 years working on creating the specialized thorium-doped fluoride crystals that enabled their earlier breakthrough. These crystals were not only difficult to grow but also required a significant amount of thorium—up to 1 milligram, which is a substantial quantity given the global scarcity of thorium-229.

Now, the team has found a simpler and more cost-effective solution. By electroplating a minute amount of thorium onto stainless steel, they have achieved the same results using 1,000 times less thorium. The resulting product is a small piece of steel, which is much tougher and more practical than the fragile crystals.

Potential Applications and Future Implications

The impact of this breakthrough extends beyond just timekeeping. Thorium-based nuclear clocks could play a crucial role in satellite-free navigation, particularly in environments where GPS signals are unavailable or unreliable. For example, submarines operating deep underwater or spacecraft traveling in deep space could benefit from these advanced clocks, which are more resistant to environmental disturbances.

Additionally, the development could lead to improved synchronization of power grids and communication networks. It might also enhance radar systems and other technologies that rely on precise timing.

Experts in the field have praised the work, noting its potential to reduce the cost and complexity of future thorium-based nuclear clocks. Makan Mohageg, optical clock lead at Boeing Technology Innovation, highlighted the importance of innovations like these for aerospace applications. Similarly, Eric Burt of NASA’s Jet Propulsion Laboratory emphasized the potential of thorium nuclear clocks to revolutionize fundamental physics measurements, including tests of Einstein’s theory of relativity.

Looking Ahead

The research, published in Nature, marks a major milestone in the quest for more accurate and reliable timekeeping. As the team continues to refine their method, the future of nuclear clocks looks brighter than ever. With further advancements, these clocks could become a common feature in everyday devices, from smartphones to satellites, transforming how we navigate and interact with the world.