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Spin-Polarizing Cold Sodium Atoms in a Strong Magnetic Field

K. M. R. van der Stam·A. Kuijk·R. Meppelink·J. M. Vogels·P. van der Straten
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Abstract

The efficiency of evaporative cooling, which is used for the creation of a Bose Einstein condensate, depends strongly on the number of particles at the start of the evaporation. A high efficiency can be reached by filling the magneto-optical trap with a large number of atoms and subsequently transferring these atoms to the magnetic trap as efficiently as possible. In our case (for sodium) this efficiency is limited to 1/3, because the magnetic substates of the F = 1 state, which is used in the trapping process, are equally populated. This limit can be overcome by spin-polarizing the sample before the transfer. For sodium atoms, however, the improvement is very small when it is done in a small magnetic field due to the large number of optical transitions in combination with the high optical density. In this article we describe spin-polarizing sodium atoms in a high magnetic field. The transfer efficiency is increased by a factor of 2. The high magnetic field makes the process also more robust against variations in the magnetic field, the laser frequency and the polarization of the laser beam.

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K. M. R. van der Stam, A. Kuijk, R. Meppelink, J. M. Vogels, P. van der Straten. 2006-03-30. Spin-Polarizing Cold Sodium Atoms in a Strong Magnetic Field. https://doi.org/10.1103/physreva.73.063412

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