Generation of an intense and slow caesium atomic beam with a two-dimensional magneto-optical trap (2D-MOT)

Full text: We will present the design and performances of a novel length-tuneable 2D-MOT used to load a continuous atomic fountain clock. The simple optical configuration, using metal-coated retro-reflecting prisms instead of mirrors and quarter-wave plates, saves space and laser power by recycling the cooling beams. The length of the MOT cooling zone can be varied by changing the number of prisms. This source of cold atoms (∼ 25 m.s-1) has been characterized on an experimental atomic fountain by measuring the flux of caesium atoms after their ballistic flight for three different lengths of the 2D-MOT cooling zone. For each length of the cooling zone, we optimized the 2D-MOT parameters: magnetic field gradient of the trap, power and frequency detuning of the cooling beams. We obtained the highest fountain flux (1.2.1010 at.s-1 captured by a moving molasses) for a 9 cm long MOT length, an improvement by a factor of three compared to the standard length (12 cm) of the previous 2D-MOT version. (author)