We report on the Bose-Einstein condensation of metastable Helium-4 atoms using a hybrid approach, consisting of a magnetic quadrupole and a crossed optical dipole trap. In our setup we cross the phase transition with 2 × 10 6 atoms, and we obtain pure condensates of 5 × 10 5 atoms in the optical trap. This novel approach to cooling Helium-4 provides enhanced cycle stability, large optical access to the atoms and results in production of a condensate every 6 seconds -a factor 3 faster than the state-of-the-art. This speed-up will dramatically reduce the data acquisition time needed for the measurement of many particle correlations, made possible by the ability of metastable Helium to be detected individually.
Many predictions of Doppler cooling theory of two-level atoms have never been
verified in a three-dimensional geometry, including the celebrated minimum
achievable temperature $\hbar \Gamma/2 k_B$, where $\Gamma$ is the transition
linewidth. Here, we show that, despite their degenerate level structure, we can
use Helium-4 atoms to achieve a situation in which these predictions can be
verified. We make measurements of atomic temperatures, magneto-optical trap
sizes, and the sensitivity of optical molasses to a power imbalance in the
laser beams, finding excellent agreement with the Doppler theory. We show that
the special properties of Helium, particularly its small mass and narrow
transition linewidth, prevent effective sub-Doppler cooling with red-detuned
optical molasses.Comment: 8 pages, 5 figure
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