A cesium fountain frequency standard: preliminary results

• Published in: IEEE transactions on instrumentation and measurement 1995-04, Vol.44 (2), p.128-131
• Main Authors: Clairon, A., Laurent, P., Santarelli, G., Ghezali, S., Lea, S.N., Bahoura, M.
• Format: Article
• Language: English
• Subjects: Atom optics; Atomic clocks; Atomic measurements; Density measurement; Exact sciences and technology; Frequency measurement; Laboratories; Local oscillators; Magnetooptic effects; Measurements common to several branches of physics and astronomy; Metrology; Metrology, measurements and laboratory procedures; Noise measurement; Physics; Stability; Time and frequency; Units and standards
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/19.377790

An atomic frequency standard based on a fountain of cold cesium atoms has been in operation in our laboratory for a few months. Ramsey fringes as narrow as 0.7 Hz have been obtained. The short-term frequency stability, measured against an H-maser, is 3 10/sup -13/ /spl tau//sup -1/2/, probably limited by the local oscillator frequency noise. A preliminary evaluation of some systematic effects shows that cold collisions will be the limiting effect for long-term stability and accuracy. Measurements of this shift presented here, using a magnetooptical trap, show that at low density an uncertainty of about 10/sup 15/ is obtained. Under these conditions, the number of atoms is large enough to allow a potential stability of 10/sup -13/ /spl tau//sup -1/2/ to be reached. When optical molasses is used, the initial density is lower and collisional effects are reduced by a factor of three.< >