Atoms In Magnetic Trap Research Articles

Comparison of two absorption imaging methods to detect cold atoms in magnetic trap**Project supported by the National Natural Science Foundation of China (Grant Nos. 61227902 and 61121003) and the National Defense Basic Scientific Research Program of China (Grant No. B2120132005).

Two methods of absorption imaging to detect cold atoms in a magnetic trap are implemented for a high-precision cold atom interferometer. In the first method, a probe laser which is in resonance with a cycle transition frequency is used to evaluate the quantity and distribution of the atom sample. In the second method, the probe laser is tuned to an open transition frequency, which stimulates a few and constant number of photons per atom. This method has a shorter interaction time and results in absorption images which are not affected by the magnetic field and the light field. We make a comparison of performance between these two imaging methods in the sense of parameters such as pulse duration, light intensity, and magnetic field strength. The experimental results show that the second method is more reliable when detecting the quantity and density profiles of the atoms. These results fit well to the theoretical analysis.

Systematic study of the rf-induced evaporation of 87Rb atoms in a spherical magnetic quadrupole trap

We trap 87Rb atoms in a spherical magnetic quadrupole potential consisting of a pair of anti-Helmholtz coils. The number of trapped atoms is 2.16(7)×108, and the lifetime is 26 seconds. The number, the temperature and the size of the atoms in a magnetic trap are controlled by the forced rfevaporative cooling technique. We obtain a sub-Doppler temperature of 33.7(5) μK in these atoms at an evaporation frequency of 4.2 MHz in the magnetic quadrupole trap. We discuss the properties of the atoms in the spherical magnetic quadrupole trap and the results of the rf-evaporation process.