Fig. 1. (a) Schematic diagram of the experimental installation of the Rb fountain. There are five layers of magnetic shields to suppress the environmental magnetic field. The entire setup functions in a temperature-controlled cabinet. (b) C-field and eight sets of compensation coils. Solenoid coils and other auxiliary compensation coils construct the uniform magnetic field of the Ramsey interrogation zone and free flight zone. It has an average magnetic field of approximately 50 nT.

Fig. 2. Graphical representation of two magneto-sensitive transitions from the cooling zone at 3.19 and 3.24 m/s. Average magnetic field change of approximately 0.4 nT for a central fringe shift of approximately 5.5 Hz for the two magneto-sensitive transition fringes.

Fig. 3. Ramsey fringes for ejection velocities of 3.94, 3.97, and 4.00 m/s. The embedded image is an enlargement of Ramsey’s central fringe. From the embedded diagram, the Ramsey central fringe shifts by approximately 0.8 Hz, which corresponds to an average magnetic field fluctuation of 0.05 nT.

Fig. 4. Time-averaged magnetic field map. Measured position of the ($-1$, $-1$) magnetic-sensitive central Ramsey fringe as a function of the height above the Ramsey cavity. The origin of the horizontal axis corresponds to the center of the Ramsey cavity. The peak-to-peak variation of space magnetic field in Ramsey region is about 0.74 nT.

Fig. 5. Monitoring the central Ramsey fringe of the |F = 2, m_F = −1→|F = 1, m_F = −1〉 transition for nearly 2 days. The temporal variation did not exceed ±0.85 Hz, which corresponds to a magnetic field variation of 0.06 nT.