Time & Frequency
Home of the nation's atomic time scale, NPL is the focus for time and frequency measurements in the UK.
The UK atomic time scale is based on an ensemble of hydrogen masers and caesium atomic clocks. These are used to contribute to international atomic timescales and to provide the reference for time and frequency dissemination and monitoring within the UK. We have also developed a caesium fountain primary frequency standard to provide the top-level realisation of the SI unit of time, the second.
Unique clock steering algorithms are being developed together with methods to evaluate clock and time transfer noise processes. This work is making a crucial contribution to the development of the reference time scale for the European global satellite navigation system Galileo.
Another major area of world-class research activity is the development of a new generation of optical frequency standards, which are potentially much more accurate than microwave standards. Optical frequency standards have many potential applications, ranging from improved satellite navigation systems to sensitive tests of fundamental physical theories. In future they could even lead to the second being redefined in terms of an optical transition frequency.
Time & Frequency science areas
- Microwave frequency standards are key to dissemination of high accuracy time services to UK science, technology and industry, and to compatibility with international timescales through world-wide time transfer and clock comparison.
- NPL is the UK's centre for precise time and frequency measurement. We operate the group of atomic clocks that form the national time scale, known as UTC(NPL).
- The heart of an optical clock is a highly stable reference frequency provided by a narrow optical absorption in an atom or ion. At NPL we are developing clocks based on transitions in single trapped ions and atoms confined in an optical lattice.