Charged particle beam apparatus and method for operating the same

An accelerator system comprising:

• an accelerator for supplying a charged particle beam;
• an irradiation apparatus, which is provided with an electromagnet for scanning with the charged particle beam, for extracting the charged particle beam supplied from said accelerator;
• and
• a controller for stopping the extraction of the charged particle beam from the irradiation apparatus to an irradiation region by stopping supply of the charged particle beam from said accelerator, for changing the irradiation region of the charged particle beam by controlling the electromagnet under a condition when the extraction is stopped, and for resuming the extraction of the charged particle beam from the irradiation apparatus after changing the irradiation region by resuming the supply of the charged particle beam from the accelerator;
• wherein the controller operates so that if the charged particle beam, which is circulating in the accelerator during the stopping the of extraction of the charged particle beam from the irradiation apparatus, is sufficient for irradiation at a new irradiation region after the changing of the irradiation region, the supply of the charged particle beam in the accelerator to the irradiation apparatus is resumed;
• and
• wherein if the charged particle beam, which is circulating in the accelerator during the stopping of the extraction of the charged particle beam from the irradiation apparatus is insufficient for irradiation at the new irradiation region after the changing of the irradiation region, the supply of the charged particle beam in the accelerator to the irradiation apparatus is resumed after supplying charged particles from a charged particle generator to the accelerator.