- Nuclear clocks promise accuracy far beyond existing atomic timekeeping systems
- Thorium 229 offers a rare pathway to practical nuclear time measurement
- Ultraviolet breakthrough reduces one of the hardest barriers in nuclear clock development
A new crystal developed by Chinese scientists has broken the world record for ultraviolet light conversion, bringing nuclear clock technology closer to reality.
The fluorinated borate compound pushes laser light to a wavelength of 145.2nm, beating the previous benchmark of 150nm set by a Chinese crystal from the 1990s.
This wavelength is suitably short to meet a key requirement for ultra-precise portable nuclear clocks being developed in the United States, China, and other countries.
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Nuclear clocks – a major upgrade to GPS
Nuclear clocks keep time using vibrations inside an atomic nucleus rather than electron vibrations used in atomic clocks.
Atomic nuclei are far more stable than electrons and less affected by temperature, external vibration, and magnetic fields, meaning nuclear clocks could be 10 to 1,000 times more accurate than today’s atomic clocks.
Such precision would enable navigation in places where GPS does not work, including deep space and underwater.
Submarines currently need to surface for GPS fixes, making them vulnerable to detection – so a nuclear clock could allow them to navigate freely underwater using dead reckoning based on speed, direction, and elapsed time.
The research team, led by Pan Shilie at the Xinjiang Technical Institute of Physics and Chemistry, turned to thorium 229 for its work.
This element is special because its nucleus vibrates at a very low energy level, making it relatively easy to monitor and measure.
However, measuring it requires extremely precise UV lasers with wavelengths around 148.3nm, which have been very hard to produce.
The new crystal converts laser light to 145.2nm, still short of the target but a major step forward.
The team wrote that its work “paves the way for the practical development of the thorium 229 nuclear clock.”
If the magic number is ever achieved, the crystal could also help missiles become immune to navigation jamming, an advantage during wartime.
For spacecraft, autonomous deep space navigation without Earth-based corrections would become possible, and signals from stars, pulsars, and radio sources could also serve as navigation aids.
The work also offers a new way to design next-generation deep ultraviolet materials for various applications.
In theory, the extreme precision of nuclear clocks could enable far tighter network synchronization, potentially leading to faster internet speeds in future systems.
However, such clocks will likely not render GPS entirely redundant but will help reduce reliance on these systems if perfected.
GPS can be jammed or spoofed with fake signals, making it vulnerable during wartime, and it does not work well underwater or underground. A thorium nuclear clock would address all these limitations.
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