Progress on Optical-clock-based Time Scale at NIST: Simulations and Preliminary Real-Data Analysis
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a clock. The simulations indicate that to achieve the same performance of a continuously-operations Cs-fountain time scale, it is necessary to run an optical clock 12 min per half a day, or 1 hour per day, or 4 hours per 2.33 days or 12 hours per week. Following the simulations, the Yb optical clock at NIST were often operated on each weekday, in 2017 March-April and in 2017 October-December. The operation time ranges from a few minutes to a few hours, depending on the experimental arrangements. This paper analyzes these real data preliminarily, and discusses the results and possible problems. More data are needed to come up with a conclusion.