Compensation of the Vertical Overfocusing of the Beam during Its Extraction from U400M Cyclotron

Accelerated beams are extracts from U400M isochronous cyclotron by means of recharging on a thin carbon foil. Two passive magnetic channels are placed after the foil to correct radial dimension of the extracted beam during its passing through strong radial gradient of the fringe magnetic field. The trajectory of the beam after recharging at the foil crosses the valley-sector at an acute angle that leads to vertical overfocusing. This effect was not corrected in the original configuration of the extraction system, and led to strong aperture losses of the extracted beam. We have realized a method to compensate the vertical overfocusing of the beam by changing of the first passive magnetic channel configuration is realize.