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Accuracy evaluation of the optically pumped Cs frequency standard at NRLM

1999; Institute of Electrical and Electronics Engineers; Volume: 48; Issue: 2 Linguagem: Inglês

10.1109/19.769640

1557-9662

Ken Hagimoto, Shinichi Ohshima, Y. Nakadan, Y. Koga,

Scientific Measurement and Uncertainty Evaluation

The optically pumped cesium (Cs) frequency standard at the National Research Laboratory of Metrology, Ibaraki, Japan (NRLM), NRLM-4, was modified in various ways in order to improve frequency stability and accuracy, We determined the frequency stability by comparing the phase with that of a hydrogen maser: the Allan deviation was /spl sigma//sub y/(/spl tau/)=5/spl times/10/sup -13///spl radic//spl tau/. We estimated the frequency corrections and uncertainties due to various sources, and the total uncertainty was found to be 2.9/spl times/10/sup -14/. The frequency difference between NRLM-4 and the international atomic time (TAI) was also measured.