A magnetic lens for cold atoms controlled by a rf field

We report on a new type of magnetic lens that focuses atomic clouds using a static inhomogeneous magnetic field in combination with a radio-frequency (rf) field. The experimental study is performed with a cloud of cold cesium atoms. The rf field adiabatically deforms the magnetic potential of a coil and therefore changes its focusing properties. The focal length can be tuned precisely by changing the rf frequency value. Depending on the rf antenna position relative to the dc magnetic profile, the focal length of the atomic lens can be either decreased or increased by the rf field.