Stress Study for Conduction Cooling Superconducting Magnet for Medical Cyclotron SC240

A high stress superconducting magnet for the 200MeV superconducting isochronous cyclotron has been constructed and operated to supply 3.6 T extraction magnetic field for proton therapy by CIM Inc. Based those experiences, A 240MeV superconducting isochronous cyclotron (so call SC240) for proton therapy is under development by CIM (F. Jiang et al. , 2019). A superconducting magnet including 2 symmetry up/down split coils would be used to supply the 3.0 T isochronous extraction magnetic fields. The NbTi/Cu WIC conductor is selected to fabricate the superconducting coil. In this paper, the radial stress, hoop stress and displacement of the coil are investigated under different winding tension, cool down and Lorentz forces. Hoop stress is the most key point, the results are shown not more than 60 MPa, which meets the 80 MPa allowable requirement. Optimizing the coil stress design of SC240 can supply sufficient safety margin about lower 50% for hoop stress compared with SC200, which will minimize the risk of training times or avoid premature quench.