Low velocity, high flux, continuous source of cesium atoms

We present a 2D magneto-optical trap (MOT) that uses an innovative simple optical configuration. Instead of mirrors and quarter-wave plates we use metal-coated retro-reflecting prisms so as to recycle the optical power of the cooling laser beam. We have characterised this source for three different configurations: with and without transverse magnetic field gradient, as well as with a pusher beam to produce a 2D+-MOT. The longitudinal velocity is about 25 m·s-1, with a transverse velocity spread ≤ 1 m·s-1, while the typical atomic flux density can be as much as 1.3×1014 at·s-1·m-2 for a cesium vapour pressure of ~4×10-8 mbar in the source. We use this low velocity atomic beam, instead of thermal vapour, to load a 3D moving optical molasses that launches a continuous cold cesium fountain. We achieve a gain of a factor ~ 20 in the fountain's atomic flux.