We measure the number of atoms, N, that can be trapped in a conventional vapor cell MOT using beams that have a diameter d in the range 1-5 mm. We show that the N \propto d3.6 scaling law observed for larger MOTs is a robust approximation for optimized MOTs with beam diameters as small as $d\approx2$~mm. For smaller beams, the description of the scaling depends on how $d$ is defined. We suggest that to accurately describe the capture volume at high intensities, $d$ should be defined as the diameter where the intensity falls to $I=Isat . Using this definition, we find that $N$ scales as d6 for d<2.3~mm.
Citation: Optics Letters
Pub Type: Journals
laser cooling and trapping, magneto-optical trap (MOT)