Citation
Abstract
In order to provide frequency standards for the DSN which are more stable than presentday hydrogen masers, a research task was established under the Advanced Systems Program of the TDA to develop a 199Hg* trapped ion frequency standard. This article describes the first closed-loop operation of this standard. Mercury 199 ions are confined in an RF trap and are state-selected through the use of optical pumping with 194-nm UV light from a 792Hg discharge lamp. Absorption of microwave radiation at the hyperfine frequency (40.5 GHz) is signaled by atomic fluorescence of the UV light. The frequency of a 40.5-GHz oscillator is locked to a 1.6-Hzwide atomic absorption line of the trapped ions. The measured Allan variance of this locked oscillator is currently sigma = 4.4 X 10-12 for 20 <1 < 320 seconds, which is better stability than the best commercial cesium standards by almost a factor of 2. This initial result was achieved without magnetic shielding and without regulation of ion number.
Details
- Volume
- 42-92
- Published
- February 15, 1988
- Pages
- 13–19
- File Size
- 298.5 KB