The PTB primary clock CS3: Type B evaluation of its standard uncertainty

The CS3, a primary atomic clock with a vertical caesium beam of the Physikalisch-Technische Bundesanstalt, has been in operation since autumn 1992. A type B evaluation of its uncertainty was performed and a combined standard uncertainty of 14 . 10(-15) was obtained. The clock can now, together with others, be used to realize International Atomic Time.