Particle beam guiding system and related radiotherapy system

A method of controlling, in a particle beam guiding system, an exit energy level and an exit trajectory of a particle beam, the method comprising the steps of:

• receiving, in the particle beam guiding system, a particle beam along an incoming trajectory;
• adjusting the exit energy level of the particle beam in an attenuator of the particle beam guiding system;
• deflecting the particle beam from the incoming trajectory into an intermediate trajectory using a first beam guide of the particle beam guiding system positioned downstream of the attenuator, the first beam guide comprising a first guiding dipole and a second guiding dipole, each guiding dipole comprising two magnets for creating magnetic fields for deflecting the particle beam from the incoming trajectory into the intermediate trajectory, wherein the first guiding dipole of the first beam guide is arranged for deflecting the particle beam in a first plane, and the second guiding dipole of the first beam guide is arranged for deflecting the particle beam in a second plane, which is orthogonal to the first plane;
• deflecting the particle beam from the intermediate trajectory into the exit trajectory using a second beam guide of the particle beam guiding system positioned downstream of the first beam guide, the second beam guide comprising a first guiding dipole and a second guiding dipole, each guiding dipole comprising two magnets for creating magnetic fields for deflecting the particle beam from the intermediate trajectory into the exit trajectory, wherein the first guiding dipole of the second beam guide is arranged for deflecting the particle beam in a third plane, and the second guiding dipole of the second beam guide is arranged for deflecting the particle beam in a fourth plane, which is orthogonal to the third plane;
• and
• controlling an alignment of the exit trajectory using a beam trajectory monitoring and control unit of the particle beam guiding system positioned downstream of the second beam guide, wherein the beam trajectory monitoring and control unit comprises a first beam trajectory control disk and a second beam trajectory control disk of a particle beam attenuating material, each beam trajectory control disk being individually movable in an individual parallel plane, which is orthogonal to the incoming trajectory, and each beam trajectory control disk displaying an opening, an alignment of which opening defines the exit trajectory.