RESEARCH ON THE EFFECT OF MAGNET PARAMETERS ON THE ISOCHRONOUS FIELD OF A SUPERCONDUCTING CYCLOTRON

It is a complicated task to obtain an isochronous field of a cyclotron magnet. Due to non-linear property of iron, iterated simulation of magnet design takes a long time to get an isochronous field. As an example, for a magnet design of a 240 MeV (SC240) superconducting cyclotron, the effect of main parameters of a magnet system on the magnetic field was studied, among them the azimuthal sector width, the spiral sector angle, the gap between sectors, the depth of valley region, the position of the coil, the shape of the coil and the excited current of the superconducting coil. It was found that the azimuthal average magnetic field can be increased by any of the following methods, including enlarging azimuthal width, increasing excited current of the superconducting coil, narrowing of the gap between sectors, reducing the depth of the valley region or decreasing the distance between the coil and the mid-plane. In addition, axial oscillation frequency can be improved by increasing the spiral angle, the depth of the valley region, or decreasing the gap between sectors.