Impact of new high stability frequency standards on the performance of the NIST AT1 time scale

Abstract

The recent addition of new commercial high stability frequency standards to the National Institute of Standards and Technology (NIST) real time AT1 time scale has resulted in significant improvements in the performance of the scale. The frequency stability of the scale at one day has increased by a factor of 2 to 4 X and the stability at 100 days has improved to approximately 1 x As a result UTC (NIST) has been kept within 50 ns of UTC (Coordinated Universal Time) for the last year. Further improvements are anticipated as more high performance clocks are added to the AT1 ensemble.

Environmental factors and hydrogen maser frequency stability

“…With cavity tuning this stability can be extended to tens of days. The National Institute of Standards and Technology (NIST) has five commercially available cavity-tuned, active hydrogen masers 1 at its site in Boulder, Colorado, all of which are currently used in the NIST AT1 time scale [1]. One of the masers also is routinely used as the reference oscillator for the primary frequency standard NIST-7 [4] and for research on new technologies for primary frequency standards.…”

“…T he number of hydrogen masers being used in time scales around the world has increased significantly over the last 10 years [1]- [3]. The Bureau International des Poids et Mesures (BIPM) now uses data from more than 25 masers in the generation of International Atomic Time (TAI).…”

“…The author is with the National Institute of Standards and Technology, Time and Frequency Division, 847.5, Boulder, CO 80303 (email: tparker@bldrdoc.gov). 1 Sigma Tau Standards Corp. series 2000 cavity-tuned hydrogen masers. Commercial equipment has been identified because it would be impossible to duplicate the results without this information.…”

Le nouvel UTC(OP) fondé sur les fontaines atomiques du LNE-SYRTE

“…Par conséquent, il y a plusieurs interprétations possibles sur les objectifs de la réalisation d'un UTC(k). Dans certains cas, l'algorithme mis en place privilégie la stabilité de l'intervalle de temps unitaire (c'est-à-dire la fréquence), tout en acceptant que l'échelle de temps s'éloigne de temps à autre de l'UTC [3]. Dans le cas de UTC(OP), notre objectif est de produire un signal physique, disponible en temps réel, qui réalise au mieux l'UTC, en tenant compte du fait que les données d'écart à l'UTC ne sont accessibles qu'après un délai pouvant atteindre 40 jours, correspondant à la publication mensuelle de la Circulaire T par le Bureau international des poids et des mesures (BIPM).…”

Second generation cesium fountain primary frequency standards at NIST

“…This time scale provides the flywheel for the fountain and has a short term stability of around σ y (τ) = 1×10 -13 /τ 1/2 [3]. Since we are presently unaware of another continuously operating flywheel with greater short term stability (with the possible exception of the JPL Hg + microwave standard [4]) we find it disadvantageous to require higher short term stability in our proposed fountain while simultaneously meeting the accuracy goal of δf/f<10 -16 .…”