BNM-SYRTE Fountains: Recent Results

Abstract

Recent improvements of Bureau National de Me/spl acute/trologie Syste/spl grave/mes de Re/spl acute/fe/spl acute/rence Temps Espace (BNM-SYRTE) fountains FO1 and FO2 are described. Fractional frequency instabilities of 2.9/spl times/10/sup -14//spl tau//sup -1/2/ for FO1 and 1.6/spl times/10/sup -14//spl tau//sup -1/2/ for FO2 have been demonstrated. A preliminary estimate of the systematic frequency shifts gives an uncertainty of /spl plusmn/7.2/spl times/10/sup -16/ for FO1 and /spl plusmn/6.5/spl times/10/sup -16/ for FO2. Furthermore, we present a direct comparison between the two fountains. When a real-time measurement of the collisional shift is included, we observe a stability of the comparison of 5.0/spl times/10/sup -14//spl tau//sup -1/2/ and a frequency difference of /spl delta/=4/spl times/10/sup -16/, well within the combined uncertainties.