Ion optics for large-acceptance magnetic spectrometers: application to the MAGNEX spectrometer

The ion optics of large-acceptance magnetic spectrometers are discussed. General techniques based on a minimum of multi-purpose magnetic elements are described. The aberrations should be minimised by shaping the entrance and exit effective field boundaries of bending magnets, the residual terms being corrected by software. Field clamps, shims and surface coils (the latter to provide kinematic compensation) are also discussed. The results and formulae which we obtain are applied to the case of the large-acceptance (∼50 msr) high-resolution magnetic spectrometer “MAGNEX” at INFN-LNS Catania.