Recent improvements on the atomic fountain clock at SIOM

Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in 1016, and the best optical clock has reached a type B uncertainty below 10−18. Besides applications in the metrology, navigation, etc., ultra-stable and ultra-accurate atomic clocks have also become powerful tools in the basic scientific investigations. In this paper, we focus on the recent developments in the high-performance cold atomic clocks which can be used as frequency standards to calibrate atomic time scales. The basic principles, performances, and limitations of fountain clocks and optical clocks based on signal trapped ion or neutral atoms are summarized. Their applications in metrology and other areas are briefly introduced.

Section: Introductionmentioning

confidence: 99%

Cold atom clocks and their applications in precision measurements*

Dai¹,

Zheng²,

Liu³

et al. 2021

“…[1] Several laboratories worldwide are studying atomic fountain clock to improve its performance, which includes the two extremely important parameters, that is, frequency accuracy and frequency stability. [2][3][4][5][6][7][8] Recently, a new caesium atomic fountain clock NTSC-F2 has just been developed and put into operation at the National Time Service Center (NTSC). To evaluate the frequency uncertainty, it must be corrected for the following several frequency shifts: second-order Zeeman frequency shift, [9] collisional frequency shift, [10] gravitational red frequency shift, [11] black-body radiation frequency shift, [12] and so on.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of second-order Zeeman frequency shift in NTSC-F2*

Shi¹,

Wang²,

Bai³

et al. 2021

Caesium atomic fountain clock is a primary frequency standard, which realizes the duration of second. Its performance is mostly dominated by the frequency accuracy, and the C-field induced second-order Zeeman frequency shift is the major effect, which limits the accuracy improvement. By applying a high-precision current supply and high-performance magnetic shieldings, the C-field stability has been improved significantly. In order to achieve a uniform C-field, this paper proposes a doubly wound C-field solenoid, which compensates the radial magnetic field along the atomic flight region generated by the lead-out single wire and improves the accuracy evaluation of second-order Zeeman frequency shift. Based on the stable and uniform C-field, we launch the selected atoms to different heights and record the magnetically sensitive Ramsey transition |F = 3, mF = –1〉 → |F = 4, mF = –1〉 central frequency, obtaining this frequency shift as 131.03 × 10−15 and constructing the C-field profile (σ = 0.15 nT). Meanwhile, during normal operation, we lock NTSC-F2 to the central frequency of the magnetically sensitive Ramsey transition |F = 3, mF = –1〉 → |F = 4, mF = –1〉 fringe for ten consecutive days and record this frequency fluctuation in time domain. The first evaluation of second-order Zeeman frequency shift uncertainty is 0.10 × 10−15. The total deviation of the frequency fluctuation on the clock transition induced by the C-field instability is less than 2.6 × 10−17. Compared with NTSC-F1, NTSC-F2, there appears a significant improvement.

“…Atomic clocks are used in many different fields, such as navigation, time keeping, and fundamental physics research. [1,2] Consequently, many kinds of atomic clocks have been developed, such as chip-scale atomic clock, [3] hydrogen maser, [4] pulsed optical pump atomic clock (POP) based on vapor cell, [5,6] microwave Hg ion clock, [7,8] integrating sphere cold atom clock, [9,10] atomic fountain, [11][12][13] and optical clock. [14][15][16] Although atomic fountains are the contemporary primary frequency standard and an ultra-high precision of 10 −19 is achieved for the optical clock, [14] the compact microwave atomic clocks play an important role in global positioning systems due to their small size and good frequency stability.…”

Section: Introductionmentioning

confidence: 99%

Development of the integrated integrating sphere cold atom clock*

Yu¹,

Meng²,

Ye³

et al. 2019

We develop an integrated integrating sphere cold atom clock (ISCAC), which mainly consists of physical package, laser system, microwave source, and electronics. This compact system is more stable and reliable than the previous version. The experimental results show that the short term frequency stability of 5.4 × 10 − 13 τ − 1 / 2 and 2.9 × 10−15 at 1-day integrating time are achieved.