Abstract: 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?.