Increasement of effective number of detected atoms in KRISS-F1(Cs) fountain clock by optical pumping

We have performed optical pumping (OP) technique to increase the effective number of detected atoms in the KRISS-F1 (Cs) fountain clock using two laser frequencies. The maximum gain of detected signal is 3.5. We anticipate the short-term stability of KRISS-F1(Cs) will be improved with OP.