We demonstrate the generation of a slow ytterbium atomic beam with a transverse momentum width of 0.44(6) times the photon recoil associated with Bragg diffraction, and a flux of 6.7 ( 9 ) × 10 6 atoms/s. This is achieved by applying momentum filtering through a long-lived metastable state to atoms prepared in a slow beam via two-dimensional transverse laser cooling. The resulting narrow momentum distribution enables efficient quasi-Bragg diffraction, which we exploit to realize a Bragg interferometer. These results mark a significant step toward continuous, high-precision, and magnetically insensitive angular rate measurements using cold alkaline-earth(-like) atomic beams.
We discuss the implementation and characterization of the source of a slow, intense, and collimated beam of rubidium atoms. The cold atomic beam is produced by two-dimensional magneto-optical trapping in directions transverse to the atomic beam axis and unbalanced Doppler cooling in the axial direction. The vacuum design allows use of relatively low laser power and a considerably simplified assembly. The atomic beam has a high flux of about $2\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}∕\mathrm{s}$ at a total cooling laser power of
55mW. It has a narrow longitudinal velocity distribution with mean velocity
15m∕s with full width at half maximum
3.5m∕s and has a low divergence of
26mrad. The high flux enables ultrafast loading of about
1010 atoms into a three-dimensional (3D) magneto-optical trap within 500 ms. The variation of the atomic beam flux was studied as a function of the rubidium vapor pressure, cooling laser power, transverse cooling laser beam length, detuning of the cooling laser, and relative intensities of the cooling beams along the atomic beam axis. We also discuss a detailed comparison of our measurements of the cold atomic beam with a 3D numerical simulation.