Progress of the Atomic Fountain Clock KRISS-Fl

We present the current status of the atomic fountain clock KRISS-F1 under development at KRISS. An ultrastable cryogenic sapphire oscillator (CSO) is used as a local oscillator of the fountain. The short-term stability measured with the CSO reaches 3.2×10
^-14
at an averaging time of 1 s. The systematic uncertainty of the fountain is expected to reach low 10-
¹⁶
level. The evaluation of the distributed cavity phase shift and its uncertainty is currently underway.