Detailed study of a transverse field Zeeman slower

We present a thorough analysis of a Zeeman slower for sodium atoms made of permanent magnets in a Halbach configuration. Due to the orientation of the magnetic field, the polarization of the slowing laser beam cannot be purely circular, leading to optical leakages into dark states. To circumvent this effect, we propose an atomic state preparation stage that is able to significantly increase the performance of the Zeeman slower. After a careful theoretical analysis of the problem, we experimentally implement an optical pumping stage leading to an increase in the magneto-optical trap loading rate by 3.5. Such a method is easy to set up and could be extended to other Zeeman slower architectures.