Guidage d'un faisceau de particules chargées à travers une chaîne de solénoïdes cylindriques et toroïdaux alternés
The present paper is devoted to analyzing the magnetic fringe-field and space-charge effects on a beam of nonrelativistic electrons crossing a sequence of cylindrical and toroidal solenoids, as may be found in an electron cooler. The investigation is mainly aimed at searching for suitable conditions that ensure conservation of the axial symmetry of a given beam throughout the whole system. The need for a vertical steering field, in addition to the longitudinal one provided by each toroidal coil, is emphasized and its form determined. A suitable choice of the angular extent of a torus is shown to suppress axis vibrations at the entrance of the following sector. Finally, the transverse temperature of a cylindrical beam is calculated after specifying the appropriate distribution function.