Initial Operational Experience with a Mercury Ion Storage Frequency Standard

Precision measurements with non-laser-cooled trapped ions

“…The development of the trapped-ion frequency standards was pioneered by Jardino and co-workers of the Laboratoire de l'Horloge Atomique [76] and by Cutler and co-workers of Hewlett-Packard [77] at the beginning of the 1980s. Since then, much of the development work on 199 Hg + standards has taken place at the NASA Jet Propulsion Laboratory.…”

“…This is why the JPL standard is operated in a quite large magnetic field (B ∼ 50-80 mG) compared with hyperbolic-trap standards (e.g. B ∼ 100 nT for the HP trap [77]). A lower magnetic field would be desirable to reduce the sensitivity of the standard to magnetic field fluctuations (see the discussion following equation (15)).…”

Future Slow-atom Frequency Standards

“…A 40,5GHz microwave clock based on the Ig9Hg+ ion ( I = 1/2) was constructed by Cutler et al [66], and its short-term frequency stability is shown in Figure 1. Approximately 2 x lo6 ions were stored in the trap, their space charge being sufficient to repel ions from the trap center, thereby producing substantial micromotion.…”

Hydrogen maser performance at the United States Naval Observatory and the Naval Research Laboratory

“…The USNO Master Clock is a system of several hydrogen masers, cesium beam and mercury ion frequency standards. USNO has up-graded its time scale and in recent years has added an NRL designed 48 channel long term clock measurement system[l], a new full Kalman filter based clock ensemble [2], three trapped Mercury Ion devices [3] and fourteen Hydrogen masers [4, 51. NRL has been in the forefront of advanced clock development for a variety of DOD systems including the USNO Master Clock upgrade program and the Global Positioning System (GPS) atomic clock development program [6]. Hydrogen masers serve as the primary frequency standard in the NRL clock test facility.…”