The invention relates to a
cyclotron which can produce a beam of accelerated charged particles that are intended for the
irradiation of at least one target (200). The inventive
cyclotron consists of a
magnetic circuit which essentially comprises: an
electromagnet with at least two poles (1, 1′), namely an upper pole (1) and a
lower pole (1′), which are disposed symmetrically in relation to a mid-plane (110) which is perpendicular to the central axis (100) of the
cyclotron and which are separated by a gap (120) containing the circulating charged particles and return flux (2) in order to close the aforementioned
magnetic circuit; and a pair of main induction coils (5, 5′) which are used to create an essentially-constant main
induction field in the gap between poles 1 and 1′. The invention is characterised in that it comprises means of
centring the above-mentioned beam, consisting of at least one pair of bucking coils (6, 7) which are supplied by an electrical source (8) and which can modulate the intensity of the main
induction field produced by the main coils (5, 5′), in order to increase the intensity of the
induction field in a first area of the cyclotron and to reduce the intensity of the induction field in a second area of the cyclotron, which is diametrically opposed to the central axis (100) of the cyclotron.