Accuracy evaluation of the KRISS-F1 fountain clock

A number of cesium atomic fountain primary frequency standards (PFS) realizing the International System (SI) second are contributing to the International Atomic Time (TAI). The accuracy of recent Cs fountain frequency standards reach low 10
⁻¹⁶
level [1-3]. Since 2010 we have been developing a Cs/Rb dual fountain frequency standard, KRISS-F1 [4]. Currently we operate KRISS-F1 as only a Cs fountain standard.