Recent progress of an atomic fountain frequency standard NMIJ-F1 (2006 – 2007)

We review the current status of development of NMIJ-F1 for the recent two years. We have performed frequency measurement a few times per year with a combined (Type A, Type B) uncertainty of 3.9times10
^-15
. For more frequent contribution to keep International Atomic Time (TAI), optics and microwave system have been modified.