First accuracy evaluation of the NRC-FCs2 primary frequency standard

We report the first accuracy evaluation of NRC-FCs2, an atomic fountain clock developed at the National Research Council Canada. The short term stability at high atomic density is 1.1 x 10(-13) at 1 second of averaging time. The typical overall fractional type B uncertainty is 2.3 x 10(-16). GNSS-based frequency comparisons of NRC-FCs2 with the SI second, as reported by the BIPM over fourteen months, give a fractional frequency difference of -2.4(3.7) x 10(-16).