Fig. 1. (a) Scheme of the 2D-HP MOT. (b) Generation scheme of the collimating hollow beam by use of an axicon.

Fig. 2. (a) Three-dimensional view of the transparent MOT system. (b) Section view of the vacuum sealing arrangement.

Fig. 3. Fluorescence pictures of cold atoms in the MOT at four axial-laser conditions. (a) No axial laser beams. (b) Pushing beam only. (c) Hollow beam only. (d) Hollow beam and pushing beam.

Fig. 4. Tunable axial velocity of the cold cesium beam. (a) Calculated atomic beam velocity as a function of the pushing power with different detunings. (b) Experimental data showing the variation of the mean axial velocity vz with the power of −7Γ (black square), −5Γ (red circle), and −3Γ-detuned (blue triangle) pushing beam. (c) Experimental data showing the variation of the axial velocity distributions with the power of a −5Γ-detuned pushing beam.