Transforming global positioning, navigation and timing

3 minute read

NPL has developed and tested a miniaturised Atomic Fountain Clock that promises to make the world’s most accurate timekeeping technology smaller, simpler and more widely accessible.  

A paper, published in Applied Physics Letters [Miniaturized atomic fountain clock | Applied Physics Letters | AIP Publishing], demonstrates the operation of a miniaturised atomic fountain clock with a radically redesigned and simplified physics package.  

This innovation aims to address critical challenges in Positioning, Navigation and Timing (PNT) for sectors ranging from telecommunications and finance to space.  

Atomic fountain clocks have long been the gold standard for precision, underpinning international time scales and enabling GPS and secure communications. However, their size, complexity and cost have restricted deployment to only a handful of highly specialised national laboratories. 

NPL’s new design aims to change that model. The physics package, which is the ultra-high vacuum system where the atoms are collected, launched, and interrogated, is reduced in volume by a factor of 20 compared to NPL’s caesium fountain primary frequency standards. “That’s taking it from barely being able to fit though a doorway, to something one could pick up and carry with one arm,” said Dr Sam Walby, the lead author of the paper. A fountain clock derives its precision from the time the atoms spend between passes through the microwave cavity on their way up and down in the fountain. Despite the miniaturisation, this time is very similar to that of the full-sized fountains. The mini-fountain achieves stability of one part in 10¹⁵ after several days of averaging, comparable to full-scale systems. 

In addition to shrinking the physics package, simplified optics and the use of commercial fibre-coupled components ensure low maintenance and high uptime, making it practical for real-world environments. 

This miniaturised clock is designed to serve as an ultra-stable holdover solution, capable of maintaining timing errors of less than two nanoseconds per month, and as a secondary frequency standard realising the SI second. These capabilities are vital to meet needs of national position, navigation and timing resilience, especially as global infrastructure faces increasing threats from GNSS disruptions and cyberattacks. 

“By radically simplifying and shrinking the atomic fountain, we’re making ultra-precise timing technology available beyond national labs,” said Walby. “This opens new possibilities for resilient infrastructure and next-generation navigation.” 

Future developments will focus on further miniaturisation of optics and electronics, enabling deployment in mobile platforms and remote locations. 

 

08 Jan 2026