State selection in a bipolar gradient magnet for a high C-field cesium beam resonator

In Cs beam frequency standards it is essential to achieve a large population difference between the F=4 and F=3 hyperfine levels. For this purpose selection systems with 2N-polar gradient magnets are often used. An advantage of this method is its velocity selectivity, which can be exploited to obtain a velocity distribution centered on reasonably slow atoms (i.e. 100 m/s). This reduces velocity-dependent biases, like second order Doppler and phase shift. In this paper we describe a state selection system with bipolar permanent magnets to be used in the cesium beam tube at the Politecnico di Torino. An experimental apparatus was realized to measure the deflection of cesium atoms. Results are compared with data obtained by numerical analysis