Patent ID: 6859741

Claim:
Apparatus for adapting the size of an ion beam spot, having the following features: a raster scanning device composed of raster scanning magnets ( 20 ) for raster scanning the ion beam ( 19 ), quadrupole magnets ( 10 ) determining the size of the ion beam spot, which quadrupole magnets ( 10 ) are arranged directly in front of the raster scanning magnets ( 20 ), two magnet power supply units ( 18 ) for the quadrupole doublet of the quadrupole magnets ( 10 ) determining the size of the ion beam spot, and a control loop for providing current correction values, by comparing desired and actual values of the prevailing dimension of the beam, for two magnet power supply units ( 18 ) of the quadrupole doublet of the quadrupole magnets ( 10 ) determining the size of the ion beam spot, for defined homogenization and/or for defined variation of the size of the ion beam spot during beam extraction and/or from measuring cycle to measuring cycle and/or from beam position to beam position, the apparatus having a control and read-out module (SAMD) that controls and reads out a denser ion beam position raster with, at the same time, a smaller ion beam spot size in the edge region ( 3 ) than in the volume region ( 4 ) of a tumour.