Particle beam irradiation system and method for controlling the particle beam irradiation system

A particle beam irradiation system comprising:

• a particle beam generation part;
• a particle beam irradiation part where a charged particle beam that is generated in the particle beam generation part is irradiated on an irradiation target and;
• an irradiation control part that controls the charged particle beam to be irradiated;
• wherein the particle beam irradiation part comprises:
• a beam scanner that scans the charged particle beam laterally in two dimensions that is perpendicular to the irradiation direction of the charged particle beam;
• and a beam diameter changer that changes the beam diameter of the charged particle beam;
• wherein the irradiation control part comprises:
• an energy setting controller that sets the energy of the charged particle beam;
• a beam scanning controller that controls the beam scanner;
• and
• a beam diameter controller that controls the beam diameter changer;
• wherein the irradiation control part sets the beam diameter of the charged particle beam by the beam diameter controller to be a first beam diameter, the charged particle beam is scanned step-wise by the beam scanning controller so as to irradiate the charged particle beam on a predetermined region of the irradiation target, after that, the beam diameter of the charged particle beam is set by the beam diameter controller to be a second diameter that is different from the first beam diameter, and the charged particle beam is scanned step-wise by the beam scan controller so as to control the charged particle beam to irradiate on a region that is overlapped with at least a part of the predetermined part of the irradiation target.