Patent ID: 6476403
Filing Date: 2002-11-05
Classification: A61N,G21K

Abstract:
Gantry with an ion-optical system comprising:a first bending magnet (1) with a bending angle in the range of 40Â° to 45Â° for bending an ion beam (4) off an axis (7) of rotation of said gantry; a second bending magnet (2) with a bending angle identical to the bending angle of the first bending magnet (1) for bending said ion beam (4) parallel to said axis (7) of rotation of said gantry (5); a third bending magnet (3) with a bending angle in the range of 45Â° to 90Â° for bending said ion beam (4) toward an intersection (6) of said ion beam (4) with said axis (7) of gantry (5) rotation, wherein the intersection (6) point is called the isocentre (10); characterized in that said gantry further comprises a horizontal scanner magnet (11) positioned upstream said third bending magnet (3) for horizontal scanning of said ion beam (4) in a plane perpendicular to the beam direction; a vertical scanning magnet (12) positioned upstream said third bending magnet (3) for vertical scanning of said ion beam (4) in a plane perpendicular to the beam direction; at least six quadrupole magnets (22-27) with adjustable excitation positioned downstream to said first bending magnet (1) and upstream said scanning magnets (11, 12), wherein the quadrupole magnets provide: a fully achromatic beam transport from the gantry entrance (30) to the isocentre (10); a control of the size of said ion beam (4) in the isocentre (10) according to a pre-defined beam-size pattern; and the size of said ion beam (4) in the isocentre (10) and the spot-shape of said ion beam (4) in the isocentre (10) which is independent from the angle of gantry (5) rotation, wherein the gantry (5) can be rotated by any angle between 0Â° and 360Â° with respect to a fixed beam transfer line connecting an accelerator with the gantry (5) and wherein said ion beam (4) coming from said fixed beam transfer line and entering said gantry (5) has different emittances in the horizontal and vertical planes of said fixed beam transfer line.