The PHARAO project: towards a space clock using cold cs atoms

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• 作者：Simon ; E. ; Laurent ; P. ; Santarelli ; G. ; Clairon ; A. ; Lemonde ; P. ; Salomon ; C. ; Dimarcq ; N. ; Petit ; P. ; et. al.
• 刊名：Acta Astronautica
• 出版年：1997
• 出版时间：June, 1997
• 年：1997
• 卷：40
• 期：12
• 页码：837-841
• 全文大小：436 K

文摘

For several years, the “BNM-Laboratoire Primaire du Temps et des Fréquences” has worked on a cold atom frequency standard. With a cesium atomic fountain a resonance line width of 700 mHz has been obtained leading to a short-term stability of 2 × 10⁻¹³ τ⁻ down to 2 × 10⁻¹⁵ at 10⁴ s. A first evaluation of the fountain accuracy has been performed resulting in an accuracy of 3 × 10⁻¹⁵, three times better than previously achieved with thermal beams frequency standards. In the atomic fountain, gravity limits the interaction time to 1 s, hence the resonance line width to 0.5 Hz. A factor of 10 reduction in the line width could be obtained in a micro-gravity environment. The “Centre National d'Etudes Spatiales” (the French space agency), the “BNM-Laboratoire Primaire du Temps et des Fréquences”, the “Laboratoire de l'Horloge Atomique” and the “Laboratoire Kastler Brossel” have set up a collaboration to investigate a space frequency standard using cold atoms: the PHARAO project. A microgravity prototype has been constructed and operated first in the reduced gravity of aircraft parabolic flights in May 1997. It is designed as a transportable frequency standard. The PHARAO frequency standard could be a key element in future space missions in fundamental physics such as SORT (solar orbit relativity test), detection of gravitational waves, or for the realization of a global time scale and a new generation of positioning system.