9 November 2015
Three atomic fountains are operational at SYRTE:
FO1 which has been the first 133Cs fountain to be constructed and exploited in time-frequency metrology. Its vacuum chamber is equipped with test tools dedicated to measurement of the Stark effect or of the blackbody radiation shift, and it has also been exploited to qualify the space clock PHARAO.
FO2 is a dual fountain, unique in the world, operating simultaneously with 133Cs and 87Rb atoms. FO2 has demonstrated the record of stability of 1.6x10-14 at 1 s. This dual fountain has allowed a very precise measurement of the Rb87 clock transition frequency, which is one of the secondary representations of the SI second, and to date the only one to participate to its definition. Besides, the comparison of the transition frequencies of the two species provides a test of the stability of the fundamental constants, such as the fine structure constant.
FOM is a transportable 133Cs fountain issued from the transformation of a prototype of the space clock PHARAO. It has operated in several laboratories in France and in Europe to realize absolute frequency measurements in the optical domain (1S-2S transition in atomic hydrogen at MPQ in Munich, Germany, clock transition of the Ca+ ion at the Innsbruck university, Austria), to test performances of techniques of time transfer (time transfer by laser link T2L2 at the observatory of Côte d’Azur, close to Grasse, various comparisons by GPS CV or GPS PPP), or else to qualify the flight model of PHARAO at CNES, Toulouse.
In practice, these three fountains at SYRTE measure the frequency of a common reference issued from a cryogenic microwave oscillator cooled down to liquid helium temperature developed by the UWA (University of Western Australia). This ultrastable oscillator (stability at one second of a few 10-15) is phase locked on one of the H-masers of the laboratory. The signal thus generated serves as reference to most of the other experiments in the laboratory. The local distribution of the signal is ensured by stabilized optical fiber links.
In practice, these three fountains at SYRTE measure the frequency of a common reference issued from a cryogenic microwave oscillator cooled down to liquid helium temperature developed by the UWA (University of Western Australia). This ultrastable oscillator (stability at one second of a few 10-15) is phase locked on one of the H-masers of the laboratory. The signal thus generated serves as reference to most of the other experiments in the laboratory. The local distribution of the signal is ensured by stabilized optical fiber links.
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