A design of a rotating gantry for non-symmetric ion-therapy beams

An ion-optical design of a gantry for transport of ion beams having different emittances in the horizontal and vertical plane is presented. The ion-optical constraints making the beam spot at the gantry exit independent from the angle of gantry rotation are derived analytically. The generally formulated constraints are applied to an isocentric normal-conducting gantry transporting the beams with maximum beam rigidity of 6.6 Tm (e.g. 430 MeV/u carbon beam with a penetration range of 30 cm in water). The gantry is equipped with a two-direction magnetic raster scanning system. The ion-optical properties of the gantry are illustrated by computer simulations performed by the TRANSPORT code.