The Magnesium Frequency Standard

Abstract

We report a complete description of a frequency standard based on the 3P1-3P0 24Mg transition at 601 GHz; in particular the metastable atomic source, the Ramsey-type interaction region, the submillimetric frequency synthesizer and the frequency-control loop are described both theoretically and experimentally. The main experimental results concerning the operation of the atomic beam, the Ramsey signal intensity and width versus some important parameters and the signal-to-noise ratio, with and without optical pumping, are reported and compared with theoretical predictions. The clock transition frequency has been measured with respect to UTC (IEN) with an uncertainty of ± 1 × 10-12; at present the frequency instability reaches the value of 2 × 10-13 for counting times of 3 000 s and the repeatability the level of 3 × 10-13. The accuracy budget is also reported and discussed as are possible improvements of the present prototype.