Design and operation of a transportable 87Rb atomic fountain clock

Abstract

A transportable fountain clock with high reliability is important for high-precision time-frequency measurements. Because of its relatively small cold atoms’ collision frequency shift and ease of attaining high quantum state preparation efficiency, the rubidium atomic fountain clock has an indicated higher stability and reliability. This paper reports the design and operation of a transportable rubidium atomic fountain clock developed by the Shanghai Institute of Optical and Fine Mechanics, Chinese Academy of Science. After being transported more than 1000 km from Shanghai to the Changping Campus of the National Institute of Metrology, China, the optical platform and other hardware of the fountain clock did not need to be adjusted. The rubidium fountain clock maintained a stability of 4.0 × 10−13τ1/2, reaching 5.0 × 10−16 at 300 000 s. After transportation, the rubidium fountain clock and a cesium fountain clock (NIM5) were operated together against the reference frequency of a hydrogen maser. In three separate operating periods, over a total of nearly three months, the average frequency repeatability of the rubidium fountain was less than 3.8 × 10−15.

Integrated, reliable laser system for an 87Rb cold atom fountain clock

“…The laser frequency of the cooling component is locked to the crossover The overall topological design of the optical path is nearly identical to that of the previous fountain clock. [13,14] We di-vided the laser system into four modules according to function to facilitate the replacement of modules and satisfy the maintainability requirement. Figure 1 is a schematic of the laser system.…”

“…Consequently, our laser system is more compact than previous schemes and mechanically reliable. [2][3][4][5][6][7][8][9][10][11][12][13][13][14][15][16][17][18][19][20][21][22]…”

“…In the cooling module, a distributed Bragg reflector 013202-2 (DBR) laser diode is chosen as the seed laser for its compact size and high mechanical stability compared with the external-cavity diode laser, typically used in frequency standards. [13,14,[23][24][25][26][27] The output power of the DBR laser diode is approximately 100 mW. After passing through an optical isolator with 60 dB isolation, the laser beam is divided into two components by a polarization beam splitter.…”

“…Long-term tests of the fountain clock were conducted in Shanghai and Beijing, with performance being similar in the two cities. [13,14] In this article, we introduce an upgraded laser system with improvements to its vibrational resistance, thermal stability, and maintainability for developing a reliable, commercially available high-precision fountain atomic clock. Such a system is essential to promoting and applying high-precision cold atom quantum sensing devices, such as cold atom gravimeters, gravity gradiometers, and gyroscopes.…”

Development of Rb fountain clock for time keeping

“…Furthermore, the laser sources used for trapping and cooling 87 Rb atoms are more stable than those for trapping and cooling Cs atoms, which improves the operation robustness of fountain clocks. Thus, 87 Rb fountain clocks have attracted significant interest and have been used as secondary frequency standards and time-keeping clocks [21][22][23][24][25]. For a commercial clock, it is important to release the operating requirements.…”