Rotators for matching non-symmetric ion-therapy beams to rotating gantries

The paper deals with special ion-optical matching sections called “rotators” for matching non-symmetric beams to rotating ion-therapy gantries. General matrix analysis of the problem is formulated resulting in a specific set of ion-optical constraints that must be fulfilled by the rotator transfer matrix. Possible ways of fitting these ion-optical constraints are discussed and illustrated by several examples of suitable rotator lattices. Each lattice is representing a different type of rotator, e.g. point-to-point imaging lattice or parallel-to-point imaging lattice. Optimization of the rotator lattice with respect to its total length is discussed, and the most compact solutions are presented as well.