Realization Of First-stage Cooling Of Strontium For The Optical Lattice Clock

Optical clock is the most promising atomic clock and its uncertainty will reach to 10?1 8 theoretically, which could be the time and frequency standard of the next generation. Optical clock based on the trapping neutral atoms has a large number of atoms which is useful to improve the Signal-to Noise of the atomic spectroscopy. Besides, the lattice composed by"magic wave"can make the ground state and the excited state of atomic clock transition have the same Stark frequency shift. And then the frequency of atomic clock transition can be unchanged ultimately.It is very important to obtain the cold atomic samples in the optical clock. The stabilized laser will be locked to the atomic spectroscopy ultimately, so this spectroscopy is required to be good. That is to say, the number of those cooled atoms can be as more as possible and the temperature can be as low as possible. Finally it has played a significant role in raising the performance of the clock.In this paper, the experiment research of alkaline-earth metals Strontium(Sr) as the cold atomic sample in optical clock is reported. It has two stages to cool Sr atoms. The dipolar energy-level transition (5s2)1S0—(5s5p)1P1 whose corresponding wave-length is 461nm is used for the first-stage cooling. The transition (5s2)1S0—(5s5p)3P1 whose corresponding wave-length is 689nm is used for the second-stage cooling. We have finished the first-stage cooling of Sr atomic samples, Blue MOT in our laboratory at present. And we prepare the second-stage cooling of Strontium. Concretely, the experiment setup for the first-stage cooling of Sr is represented firstly in this paper, including the equipment of producing thermal atomic beam,lasers,Zeeman slower,Anti-Helmholtz coils for the optical-magnetic trap(MOT) et al. Based on those equipments, the first-stage cooling of Sr is realized. And then its number is measured experimentally using the method of collected fluorescence. The temperature of the cold atoms is measured using the ways of time of flight and expansion measurement. Finally, stabilizing the frequency and narrowing the line-width of 689nm laser used for the second-stage cooling is introduced. And the importance of the time controlling system about red MOT is presented briefly.