The Operation of the Atomic Fountains Developed at VNIIFTRI

We report on the operation of the cesium fountain primary frequency standard (SU-CsFO2), the rubidium fountain frequency standard (Rb5) and the pair of rubidium frequency standards (Rb1, Rb2) at the Russian metrological institute of technical physics and radio engineering (VNIIFTRI (SU)). We present measurements of their performance in long term frequency stability to be less than 2·10⁻¹⁶. The frequency of SU-CsFO2 with total B uncertainty 2.2·10⁻¹⁶ agreed well with other primary and secondary frequency standards within the uncertainty according to the Circular T data during the last 10 years.