Yb optical lattice clock at INRIM

The Unit of Time in the International Systems of Units is realized at the relative frequency accuracy level of few parts in 10^-16 by laser cooled Cesium fountains [1]; since 2003 INRIM has operated a laser cooled Cesium fountain with relative frequency accuracy at the level of 5×10^-16 and has contributed with this frequency standard to the generation of the International Atomic Timescale of Bureau International des Poids et des Mesures (BIPM). Since 2009 a cryogenic Cesium fountain is under operation and its metrological characterization is in progress, with a target accuracy of 1×10{-16}.