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 correctionc) 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 andf) 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 gantrys 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.
