Error analysis of the NIST optically pumped primary frequency standard

The major sources of systematic error in the NIST optically pumped primary frequency standard has been evaluated with an uncertainty of a few parts in 10¹⁴. The cavity end-to-end phase shift is the only item which differed markedly from expectations based on the design and/or measurements made during assembly. The authors think the difference is attributable to the physical dimensions of the cavity and not to its asymmetry. The device will begin to function as the US primary frequency standard, even before planned extensions to the analysis presented and improvement to the laser and servo electronics allow evaluation at its full design accuracy of one part in 10¹⁴