Caesium Beam Atomic Clock

Primary Standard for Realization of the second – Caesium Beam Frequency Standard

Photo of the Caesium Beam Frequency Standard at SCL

At SCL, the SI base unit of second is realised by using a caesium beam frequency standard based on the detection of transition between the two hyperfine levels of the ground state of the Caesium 133 atom. The output clock signal of the caesium beam frequency standard is monitored daily against the Coordinated Universal Time (UTC) via the GPS Common View Comparison.

Structure of a Caesium Beam Frequency Standard

1 PPS Signal of UTC(SCL)