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

Abstract

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.