Particle therapy gantry with an energy degrader and an achromatic final bending system

The present invention provides a movable gantry (2') for delivery of a particle beam using beam scanning technique, for example for the cancer treatment in human tissue; comprising: a) an inlet section (6) for an accelerated particle beam comprising a number of quadrupole magnets; b) a first bending section (8) and optionally a second bending section (12) comprising a number of dipole and quadrupole magnets and optionally further magnets for beam correction; c) a transfer section comprising a number of quadrupole magnets and optionally further magnets for beam correction and a degrader (D); d) a last beam bending section (16) comprising a number of separate and/or combined dipole/quadrupole/higher order multipole magnets forming an achromatic section, wherein all magnets of this achromatic last bending section (16) are located downstream of the degrader (D); any dispersion in this achromatic last bending section (16) is suppressed so that it will have a momentum acceptance of more than ±5%; e) a scanning section (15) comprising two separate or one combined fast deflection magnets (K1, K2) that deflect the beam at the iso-center in a direction perpendicular to the beam direction to perform lateral scanning; and f) a beam nozzle section (18) comprising a beam nozzle and optionally beam handling equipment, such as further beam degrading or modifying elements and/or beam quality related beam verifying elements. This combination of a degrader mounted in the gantry and a design of the gantry's beam transport magnets with a large momentum acceptance creates a possibility to increase the energy acceptance of the last bending section in the gantry and implement new dose application techniques, such as a fast change of proton energy at the patient without changing the magnetic field of the last bending section in the gantry.