Present status of primary frequency standards at NPL, India

摘要

National Physical Laboratory, India (NPLI) has developed its first Cesium atomic fountain frequency standard (NPLI-CsFl). The indigenously developed fountain frequency standard is now fully operational and its frequency is now being evaluated along with all systematic and statistical uncertainties. Seven frequency evaluation have been conducted to estimate fountain frequency with respect to TAI (International Atomic Time) and were reported to BIPM. Recently NPLI CsFl took part in live contribution of TAI evaluation. The fountain frequency is compared with the Hydrogen Maser (H-Maser) frequency which is contributing to TAI (International atomic timescale) and hence fountain frequency is evaluated with respect to the TAI. The fountain frequency is stable to few parts in 1015 at less than one day averaging time. Typical uncertainty of NPLI-CsFl ~2.8×10-15 A second generation Cs fountain is being developed in order to overcome the short comings in NPLI-CsF1.