Scanning Properties of Dipole Bending Magnets used in Ion-Therapy Gantries

In modern ion-therapy facilities, there is a trend to develop and use scanning beam delivery systems. One of the most important advantages of scanning systems is that the field-shaping material devices in the beam path are minimized or removed entirely. Scanning systems inherently provide the intensity modulated radiation fields of ion beams that allow for a much greater flexibility in tailoring the dose distribution than in the case of passive delivery systems. A study of scanning properties of dipole bending magnets is published in order to provide engineers the theoretical tool for the early stage of a scanning-system design. This study is focused on scanning properties of dipole bending magnets with pure dipole fields without any gradient. The 90°, 60°, 45° and 30° bending magnets are studied. A two-directional magnetic scanning system with two scanners, one in the horizontal and another one in the vertical plane, is considered. This 2D magnetic scanning system ensures a parallel scanning mode in both transverse planes. The ion-optical properties of 2D magnetic scanning system and the study results for dipole bending magnets mentioned above are discussed.