The description of the technical realization of a Mg beam frequency standard and the experimental results are here reported. Moreover the main sources of uncertainty are examined in order to provide the evaluation of the accuracy achievable with such a standard.
Absence of hyperfine structure and existence of a natural selection process to provide population difference and efficient detection are the ~ost attractive characteristics of a frequency standard based on the 3P1- P llm. = 0 transi tion ( ). = 498 pm in the metastable triplet of Mg. Its fre3frnc~ ha-§ been measured with respect to a Cs standard with an uncertainty of ~ 3x10 [1]; in this experiment an atomic beam rich of metastable ato~s is interrogated via a Ramsey-type technique, yielding a line Q-factor QL = 5x10 , and a 5 MHz quartz crystal oscillator is locked to the Mg transi tion via a low phase noise frequency mul tiplication chain.
Metrologia International Bureau of Weights and Measures (BIPM), find out more. Cesium Beam Atomic Time and Frequency Standards R E Beehler1, R C Mockler1 and J M Richardson1 Published under licence by IOP Publishing Ltd Metrologia, Volume 1, Number 3 Citation R E Beehler et al 1965 Metrologia 1 114 DOI 10.1088/0026-1394/1/3/004 DownloadArticle PDF Article metrics 337 Total downloads 4343 total citations on Dimensions. Permissions Get permission to re-use this article Share this article Article and author information Abstract In recognition of the October 1964 declaration of the International Committee of Weights and Measures that the physical measurement of time be based on a particular transition between two hyperfine levels in the ground state of cesium 133, a review of the characteristics of cesium beam atomic frequency standards is presented.
When observed in a cesium beam frequency standard, the hyperfine transition frequency of the atoms differs slightly from the invariant transition frequency of the unperturbed atoms at rest. The various physical and technical origins of the frequency offsets are stated. They relate to fundamental physical effects, to the method of probing the atomic resonance and to the frequency control of the slaved oscillator. The variation of the frequency offsets under a change of the value of the internal operating characteristics is considered. The sensitivity to a change of the magnetic induction, the microwave power and the temperature is given. A comparison is made of the sensitivity of cesium beam frequency standards of the commercially available type, making use of magnetic state selection, and of devices under study in which the state preparation and detection is accomplished optically.
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