The National Research Council of Canada (NRC) is currently involved in a number of research projects aimed
at improving time and frequency realization based on the accurate and precise stabilization of microwave and
optical sources on atomic and molecular transitions. Projects described in this summary will focus on the
development of a primary standard for the realization of the SI second based on a cesium atomic fountain and
a next generation standard based on an optical transition in a single trapped and laser cooled ion of strontium.
The cesium fountain is undergoing evaluations of its systematic shifts for an eventual contribution to TAI and
for a re-measurement of the absolute frequency of the strontium ion clock transition at the 10-15 level. The
main contribution to the uncertainty budget of the fountain is thought to be caused by the inhomogeneity in the
magnitude of the magnetic field in the drift region. The latest measurements of this field are presented. A new
strontium ion trap of the endcap design was completed last year. This new system has compensation electrodes
and access ports in three orthogonal directions to control the ion position and minimize micromotion. We report
preliminary results indicating improved performance of this trap over our previous rf Paul trap. As part of an
effort to reduce the systematics shifts to a minimum, the heights of the atomic standards above the geoid were
measured with an accuracy of 5 cm, corresponding to a fractional frequency uncertainty of 5 × 10-18 for the
gravitational redshift.
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