Hudson’s team spent 15 years refining the specialized thorium-doped fluoride crystals that made last year’s breakthrough possible. In the original experiments, thorium-229 atoms were bonded with fluorine in a precisely engineered structure that stabilized the radioactive material while still allowing laser light to pass through and excite the nucleus. Although the approach worked, the crystals were extremely difficult to fabricate and required relatively large quantities of the rare thorium isotope.

Figure 1. Ancient Jewelry Technique Could Enable Next-Gen Nuclear Clocks.

“We invested years into making these crystals because we believed they had to be transparent for the laser to reach the thorium nuclei,” said first author Ricky Elwell, a UCLA postdoctoral researcher. “They’re incredibly challenging to produce, take a very long time to make, and require at least 1 milligram of thorium—which is significant when only about 40 grams exist worldwide.” Elwell received the 2025 Deborah Jin Award for Outstanding Doctoral Thesis Research in Atomic, Molecular, or Optical Physics for his role in last year’s breakthrough. Figure 1 shows Ancient Jewelry Technique Could Enable Next-Gen Nuclear Clocks

In the new study, Hudson’s team deposited an extremely small amount of thorium onto stainless steel using a slight modification of a centuries-old jewelry electroplating technique. Electroplating, developed in the early 1800s, uses an electric current flowing through a conductive solution to coat one metal with a thin layer of another. In jewelry-making, for instance, gold or silver is often plated onto a less valuable metal base.

“It took us five years to learn how to grow the fluoride crystals, and now we’re achieving the same results using one of the oldest industrial methods—while using 1,000 times less thorium,” said Hudson. “The final product is essentially a small piece of steel, and it’s far more robust than the fragile crystals.”

The breakthrough came from realizing that a long-held assumption was incorrect: exciting the thorium nucleus with a laser turned out to be much easier than previously believed.

“For decades, the assumption was that thorium had to be embedded in a material transparent to the excitation light in order to observe the nuclear transition,” Hudson explained. “We showed that this simply isn’t true. We can deliver enough light into opaque materials to excite nuclei near the surface, and instead of emitting photons—as they do in transparent crystals—the nuclei emit electrons. Those electrons can be detected just by measuring an electrical current, which is about as simple as it gets in the lab.”

Thorium-based nuclear clocks and satellite-free navigation

Beyond their potential to advance communications, power-grid synchronization, and radar systems, next-generation clocks have long been viewed as a solution to a major national security challenge: navigation without GPS. If satellites were disabled—whether by hostile action or an electromagnetic storm—GPS-based navigation would fail. Submarines already rely on atomic clocks while submerged, but current clocks drift over time, forcing them to surface periodically to confirm their position. Nuclear clocks, which are far less sensitive to environmental disturbances, could provide vastly improved accuracy in such demanding conditions.

“The UCLA team’s approach could significantly reduce the cost and complexity of future thorium-based nuclear clocks,” said Makan Mohageg, optical clock lead at Boeing Technology Innovation. “Advances like this may enable more compact, highly stable timekeeping systems relevant to aerospace applications.”

“The UCLA group led by Eric Hudson has done remarkable work over more than a decade to find a practical way to probe thorium’s nuclear transition,” said Eric Burt, who leads the High-Performance Atomic Clock project at NASA’s Jet Propulsion Laboratory and was not involved in the research. “This opens a realistic path toward a viable thorium nuclear clock. These clocks could transform fundamental physics experiments, including tests of Einstein’s theory of relativity, and may one day help establish a solar-system-wide time standard—an essential step toward a permanent human presence beyond Earth.”

Source: SciTECHDaily

Cite this article:

Priyadharshini S (2025), An Ancient Jeweler’s Technique May Power the Next Generation of Nuclear Clocks, AnaTechMaz, pp. 440