Abstract: A non-superconductive cyclotron comprises a magnetic circuit comprising at least three sectors called "hills", wherein the air-gap is reduced to a size similar to that of the accelerated beam and wherein the magnetic flux is substantially concentrated. The hills are separated by spacings configured like sectors called "valleys" wherein the air-gap is a very large size so that the magnetic flux is essentially null. The magnetic circuit is further comprised of a single pair of coils which are substantially circular and surround the hills and valleys.