[en] The invention refers to a method and an arrangement for influencing and guiding a high-energy particle beam accelerated in a cyclotron. The aim is to generate a focussed particle beam at the direction of emission from the cyclotron by a large compensation of the fringing magnetic field effects of the cyclotron magnet. The arrangement has an electrostatic quadrupole singlet at the cyclotron-sided end of the beam guiding system. The axis of the escaping particle beam corresponds to the axis of the quadrupole singlet approximately. It is favourable that the quadrupole singlet electrodes have a bend adapted to the beam axis