Device and method for tuning a charged particle beam position

A method for tuning a position of a charged particle beam in a particle therapy apparatus,

• wherein the particle apparatus comprises:
• a particle accelerator to deliver a charged particle beam;
• a beam transport system to deliver the charged particle beam according to a main beam axis (Z) to a target in an isocenter plane which is perpendicular to the main beam axis (Z);
• scanning magnets to scan the charged particle beam over the target;
• a beam position detector arranged downstream of the scanning magnets and adapted to detect an X and Y position of the charged particle beam when it crosses the detector;
• a beam stopper arranged downstream of the beam position detector, the beam stopper being adapted to stop the charged particle beam when it hits the beam stopper;
• a control system configured to drive the scanning magnets to scan the charged particle beam over the target according to a pre-defined treatment field which covers a treatment surface in the isocenter plane, the control system being further capable to drive the scanning magnets to scan the charged particle beam according to a reachable field which covers a reachable surface in the isocenter plane, the reachable surface covering and being larger than the treatment surface,
• and the method comprising the steps of:
• placing the beam stopper at a position to prevent the charged particle beam from reaching at least a portion of the reachable surface and to allow the charged particle beam to reach any portion of the treatment surface,
• directing the charged particle beam to the beam stopper and meanwhile measuring an X and Y position of the charged particle beam by using the beam position detector,
• calculating a difference between a desired X and Y position of the charged particle beam and respectively the measured X and Y position of the charged particle beam when directed to the beam stopper, and
• applying a correction to the magnetic settings of the X and Y scanning magnets by taking into account the calculated difference between the desired X and Y position of the charged particle beam and respectively the measured X and Y position of the charged particle beam when directed to the beam stopper.