The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was...The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was measured in a magneto-optical trap （MOT） and during its free flight. The residual gas pressure was analyzed by a residual gas analyzer, and the pressure distribution in a vacuum chamber was numerically calculated by the angular coefficient method. The decay factor, which describes the decay behavior of cold atoms due to residual gas collisions during a free flight, was calculated. It was found that the decay factor agrees well with theoretical predictions under various vacuum conditions.展开更多
We report the initial test results of a rubidium （87Rb） space cold atom clock （SCAC）. The space-qualified ST Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the contro...We report the initial test results of a rubidium （87Rb） space cold atom clock （SCAC）. The space-qualified ST Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the control electronics. After the system is integrated, about 108 ST Rb cold atoms are captured by magneto-optical trap. The linewidth of the Ramsey fringe is about lO Hz for the free evolution time of 50ms on the ground, and the signM-to-noise ratio is measured to be larger than 300. We demonstrate a good medium-term fractional frequency stability of 1.5×10^-14@1000s in the closed-loop operation on the ground. The main effects of the noise on the stability are a/so presented, and the optimized operating parameter is analyzed for the operation of SCAC in the microgravity environment.展开更多
When the cold atom clock operates in microgravity around the near-earth orbit, its performance will be affected by the fluctuation of magnetic field. A strategy is proposed to suppress the fluctuation of magnetic fiel...When the cold atom clock operates in microgravity around the near-earth orbit, its performance will be affected by the fluctuation of magnetic field. A strategy is proposed to suppress the fluctuation of magnetic field by additional coils, whose current is changed accordingly to compensate the magnetic fluctuation by the linear and incremental compensation. The flight model of the cold atom clock is tested in a simulated orbital magnetic environment and the magnetic field fluctuation in the Ramsey cavity is reduced from 17 nT to 2 nT, which implied the uncertainty due to the second order Zeeman shift is reduced to be less than 2×10^（-16）. In addition, utilizing the compensation, the magnetic field in the trapping zone can be suppressed from 7.5 μT to less than 0.3 μT to meet the magnetic field requirement of polarization gradients cooling of atoms.展开更多
A high-performance transportable fountain clockis attractive for use in laboratories with high-precisiontime-frequency measurement requirements. This Letterreports the improvement of the stability of atransportable ru...A high-performance transportable fountain clockis attractive for use in laboratories with high-precisiontime-frequency measurement requirements. This Letterreports the improvement of the stability of atransportable rubidium-87 fountain clock because of anoptimization of temperature characteristics. This clockintegrates its physical packaging, optical benches,microwave frequency synthesizers, and electronic controlsonto an easily movable wheeled plate. Two optical bencheswith a high-vibration resistance are realized in thiswork. No additional adjustment is required after movingthem several times. The Allan deviation of the fountainclock frequency was measured by comparing it with that ofthe hydrogen maser. The fountain clock got a short-termstability of 2.3×10^-13 at 1 s and long-term stabilityon the order of 10-16 at 100,000 s.展开更多
In this article,taking advantage of the special magnetic shieldings and the optimal coil design of a transportable Rb atomic fountain clock,the intensity distribution in space and the fluctuations with time of the qua...In this article,taking advantage of the special magnetic shieldings and the optimal coil design of a transportable Rb atomic fountain clock,the intensity distribution in space and the fluctuations with time of the quantization magnetic field in the Ramsey region were measured using the atomic magneton-sensitive transition method.In an approximately 310 mm long Ramsey region,a peak-to-peak magnetic field intensity of a 0.74 n T deviation in space and a 0.06 n T fluctuation with time were obtained.These results correspond to a second-order Zeeman frequency shift of approximately(2095.5±5.1)×10^(-17).This is an essential step in advancing the total frequency uncertainty of the fountain clock to the order of 10^(-17).展开更多
基金Project supported by the Ministry of Science and Technology of China(Grant No.2013YQ09094304)
文摘The loss rate of cold atoms in a trap due to residual gas collisions differs from that in a free state after the cold atoms are released from the trap. In this paper, the loss rate in a cold rubidium-87 atom cloud was measured in a magneto-optical trap （MOT） and during its free flight. The residual gas pressure was analyzed by a residual gas analyzer, and the pressure distribution in a vacuum chamber was numerically calculated by the angular coefficient method. The decay factor, which describes the decay behavior of cold atoms due to residual gas collisions during a free flight, was calculated. It was found that the decay factor agrees well with theoretical predictions under various vacuum conditions.
基金Supported by the National Key Scientific Instrument and Equipment Development Project of China under Grant No2013YQ09094304the Youth Innovation Promotion Association of Chinese Academy of Sciencesthe National Natural Science Foundation of China under Grant Nos 11034008 and 11274324
文摘We report the initial test results of a rubidium （87Rb） space cold atom clock （SCAC）. The space-qualified ST Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the control electronics. After the system is integrated, about 108 ST Rb cold atoms are captured by magneto-optical trap. The linewidth of the Ramsey fringe is about lO Hz for the free evolution time of 50ms on the ground, and the signM-to-noise ratio is measured to be larger than 300. We demonstrate a good medium-term fractional frequency stability of 1.5×10^-14@1000s in the closed-loop operation on the ground. The main effects of the noise on the stability are a/so presented, and the optimized operating parameter is analyzed for the operation of SCAC in the microgravity environment.
基金Project supported by the Ministry of Science and Technology of China(Grant No.2013YQ09094304)the Youth Innovation Promotion Association,Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant Nos.11034008 and 11274324)
文摘When the cold atom clock operates in microgravity around the near-earth orbit, its performance will be affected by the fluctuation of magnetic field. A strategy is proposed to suppress the fluctuation of magnetic field by additional coils, whose current is changed accordingly to compensate the magnetic fluctuation by the linear and incremental compensation. The flight model of the cold atom clock is tested in a simulated orbital magnetic environment and the magnetic field fluctuation in the Ramsey cavity is reduced from 17 nT to 2 nT, which implied the uncertainty due to the second order Zeeman shift is reduced to be less than 2×10^（-16）. In addition, utilizing the compensation, the magnetic field in the trapping zone can be suppressed from 7.5 μT to less than 0.3 μT to meet the magnetic field requirement of polarization gradients cooling of atoms.
基金supported by the Ministry of Science and Technology of China(No.2013YQ09094304)the National Natural Science Foundation of China(No.11034008)
文摘A high-performance transportable fountain clockis attractive for use in laboratories with high-precisiontime-frequency measurement requirements. This Letterreports the improvement of the stability of atransportable rubidium-87 fountain clock because of anoptimization of temperature characteristics. This clockintegrates its physical packaging, optical benches,microwave frequency synthesizers, and electronic controlsonto an easily movable wheeled plate. Two optical bencheswith a high-vibration resistance are realized in thiswork. No additional adjustment is required after movingthem several times. The Allan deviation of the fountainclock frequency was measured by comparing it with that ofthe hydrogen maser. The fountain clock got a short-termstability of 2.3×10^-13 at 1 s and long-term stabilityon the order of 10-16 at 100,000 s.
基金supported by the National Natural Science Foundation of China(No.12004401)Ministry of Science and Technology of China(No.2013YQ09094304)。
文摘In this article,taking advantage of the special magnetic shieldings and the optimal coil design of a transportable Rb atomic fountain clock,the intensity distribution in space and the fluctuations with time of the quantization magnetic field in the Ramsey region were measured using the atomic magneton-sensitive transition method.In an approximately 310 mm long Ramsey region,a peak-to-peak magnetic field intensity of a 0.74 n T deviation in space and a 0.06 n T fluctuation with time were obtained.These results correspond to a second-order Zeeman frequency shift of approximately(2095.5±5.1)×10^(-17).This is an essential step in advancing the total frequency uncertainty of the fountain clock to the order of 10^(-17).
