Time and Frequency

Time scale UTC(IT)
One of the control rooms for the Italian time reference signal

The INRIM Time and Frequency Laboratory (LTF) realises the reference unit of the standard time for Italy. The Italian time scale UTC(IT) is generated with a hydrogen maser supported with commercial atomic frequency standards and atomic cesium fountains, and synchronisation satellite systems are used for the comparison of UTC(IT) with the most important NMI laboratories.

Additional information can be found here.

 

Cesium primary frequency standard
Fountain of Cs atoms

In this laboratory, we maintain the Italian primary frequency standard, based on a cesium fountain clock, nitrogen-cooled at 89 K. It has an accuracy of 2E-16, among the highest ever achieved.

This clock is used for the generation of the Italian timescale and its data are periodically sent to the Bureau International des Poids et Mesures for the computation of the International Atomic Timescale. In addition, this frequency standard is disseminated via optical fiber to several research institutes of the country, to allow precise measurements in atomic and molecular physics at unprecedented resolution.

Additional information can be found here

Optical ytterbium clock
An optical atomic clock

INRIM made an optical clock based on neutral Ytterbium atoms trapped in a lattice. The clock transition is in the optical domain, at 578 nm.

Optical frequency standards are the most promising candidates for the redefinition of the Second in the International System of Units, as they enable to achieve lower uncertainties than primary microwave clocks.

The clock developed at INRIM has an uncertainty <6E-16 and we are currently working to reduce the most relevant systematic effects, such as that due to blackbody radiation.  In parallel, a second improved system with a lower sensitivity to environmental effects is under design.

INRIM Yb optical clock participated, together with a transportable clock developed at PTB, to a proof-of-principle geodesy experiment where such devices were used as probes of the gravitational potential.

INRIM will expand its research in optical frequency standards with the development of a Sr lattice clock and with the realisation of UV laser sources with metrological traceability

Additional information can be found here

Cell clocks
Optical clock - magnetic field shielding chamber

Not only scientific experiments require accurate time/frequency references, but also several industrial applications, e.g. satellite navigation, aerospace and high-technology industry in general.

In these applications, what is required is to merge high metrological performances with properties such as compactness, reliability and low power consumption.

INRIM developed a hydrogen maser based on coherent-population trapping (CPT) and a pulsed, optically-pumped Rubidium clock, which achieves an instability of 1E-15 after 1 day of measurement. We are currently engineering its performances in order to make it compliant with the requirements of industrial applications.

Particular attention is devoted to the design of low-noise electronic synthesis chains and to digitalisation of the entire electronic apparatus.

Dissemination of time and frequency signals via optical fiber
The optical fiber dissemination of frequency in Italy

This activity demonstrated the possibility of delivering high-accuracy optical and microwave frequency signals over continental distances using the telecom optical fiber network. The accuracy and stability achievable with fiber-based dissemination outperforms state-of-the-art satellite techniques by several orders of magnitude.

It was also implemented the so-called White Rabbit technique for the sub-ns accuracy dissemination of time signals to the financial district in Milano.

A first optical fiber backbone for the distribution of optical frequencies, under operation since 2013, connects INRIM to the European Laboratory for Non Linear Spectroscopy and to the Institute of Optics in Florence; a second branch has been realised in 2015, for high-accuracy frequency dissemination to the Medicina Radiotelescopes, close to Bologna.

We are currently extending the network to the Galileo Ground Segment in Fucino; to the Institute of Optics in Pozzuoli (Naples) and to the Space Geodesy Centre in Matera​​.

Additional information can be found here

Last modified: 05/01/2018 - 14:23