A periodic focussing structure for the transport of low energy ions

Abstract For the transport of a low energy ion beam, e.g. 20 keV deuterons, a periodic focussing structure is under design. The system consists of a succession of magnetic lenses with cylindrical symmetry. The lenses are formed by permanent magnetised rings surrounding the beam pipe. The system is suitable for beams with a high emittance, 1000 mm·mrad or more, the path length difference between the trajectories of different particles is small and the beam handling is easy especially in the presence of space charge. Space charge compensation is possible. The linear and nonlinear behaviour of the beam is described and attention is given to the influence of gaps in the structure necessary for mounting vacuum pumps, bunchers etc.