Linear ion trap based atomic frequency standard

The development of a trapped ion based fieldable frequency standard with high stability for averaging times τ>1×10⁴ s is discussed. A hybrid RF/DV linear ion trap which permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields is described. ¹⁹⁹HG⁺ ions have been confined in this trap and very high Q transitions with good signal-to-noise ratio have been measured. Stabilities of 1.6×10 ^-13/√τ(50<τ<800 s) with a 160 mHz wide atomic resonance linewidth and a signal-to-noise ratio of 40 for each measurement cycle have been obtained. Atomic resonance lines as narrow as 30 mHz on the 40.5 GHz clock transition have been measured with no appreciable reduction in the ion signal. A stability of 7×10^-14/√τ is made possible by the signal-to-noise ratio and line Q of this measured transition. An analysis of fundamental sources of frequency instability indicates that a long term stability of 2×10^-16 is feasible for this device with existing technology for τ⩾10⁶ seconds