Abstract

An intense beam of cold metastable helium atoms in the 2 ³S state (He^*) is used to load a magneto optical trap (MOT). In the MOT up to 2^*10⁸ atoms are stored at a temperature of ~1 mK. This large number is obtained by collimating the metastable beam applying two-dimensional transversal laser cooling over 20 cm and deflecting it out of the ground state beam into a 2 m Zeeman slower. The loading rate is increased by a factor of 30 compared to earlier work [1]. The large atom number allows for observation of the fluorescence from the MOT with a CCD camera (wavelength 1083 nm) as well as determination of the trap size: ~6 mm diameter (2σ) in our standard MOT (δ ~ —20Γ) and about twice as large using MOT laser beams with low power in the centre. The latter procedure ensures low Penning ionization losses in the trap centre while maintaining a large capture range.

© 1998 IEEE