This is the principle behind an atomic clock. All that is needed for making a good clock is a way of detecting this frequency and using it as an input to a counter. This is like a signature for the type of material used. In this transition, the atom releases energy at a very precise frequency which is characteristic of the type of atom. Then, from this state, it goes to a lower energy state. However this kind of stability is really needed, since an error of only a few nanoseconds (billionths of a second) on the Galileo measurements would produce a positioning error of metres which would not be acceptable.Īn atomic clock works like a conventional clock but the time-base of the clock, instead of being an oscillating mass as in a pendulum clock, is based on the properties of atoms when transitioning between different energy states.Īn atom, when excited by an external energy source, goes to a higher energy state. The stability of the rubidium clock is so good that it would lose only three seconds in one million years, while the passive hydrogen maser is even more stable and it would lose only one second in three million years. The final goal of this project is to develop a device that can readily be commercialised, and so we put great effort in keeping our design and test and assembly processes friendly towards a manufacturing setting.The Galileo satellites will carry two types of clocks: rubidium atomic frequency standards and passive hydrogen masers. Meaning, pronunciation, translations and. By substituting free-space optical components by their fibre-coupled counterparts not only can we make the system significantly more compact, but also inherently more simple, stable and resilient to environmental changes. Atomic clock definition: an extremely accurate clock in which an electrical oscillator is controlled by the. Such a miniaturisation effort is made possible by exploiting the latest advances in fibre optic components, as well as semiconductor diode lasers. The expected fractional uncertainty is on the order of 10 -16: around three orders of magnitude better than commercially available microwave atomic clocks with a similar form factor, and two orders of magnitude better than the higher performance commercially available portable systems, which are ten times the size. The device is to fit in a 4-unit 19-inch rack module (50x51x15 cm), weighing under 20 kg and with a target power consumption below 100 W. Recently, transportable optical atomic clocks have started to appear, but these are still bulky, complex and power hungry systems, requiring the attention of highly skilled operators in order to function, and occupying several cubic meters of space.Īt ITCM, with the collaboration of our scientific and industrial partners, we are developing a highly compact and autonomous optical atomic clock based on a single calcium ion. In contrast, atomic clocks based on optical transitions offer much greater performances but, up until now, they have mostly been confined to highly specialised research laboratories. Devices with such a level of precision are very attractive in many areas, such as data transfer and telecommunications, geolocation networks like GPS and GNSS, earth observation measurements such as geodesy and the understanding of underground materials, as well as the advancement of fundamental physics.Ĭommercial portable atomic clock solutions exist, but they are based on microwave transitions (usually in caesium or rubidium atoms), which limits their ultimate accuracy and stability levels. Cutting edge systems being developed in metrology laboratories have shown accuracies of just a few parts in 10 -18, which for comparison corresponds to a shift of about one second over the age of the universe. Optical atomic clocks are the most accurate time-keeping instruments to date.
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