AC Loss and Thermal Analysis of a Curved DCT Super-Conducting Magnet for Carbon Ion Therapy

In this paper, a curved dipole magnet with Discrete-Cosine-Theta (DCT) coils which have compact ends and higher excitation efficiency, used for carbon ion therapy treatment facility is discussed. The dipole magnet has a bending angle of 90 degrees and a bending radius of 0.8 m. The magnet is ramped from 0 T to 2.9 T with a maximum rate of 1 T/s. However, the ramping magnetic field induces eddy current loss in metallic structure and ac loss in superconductor, resulting in temperature rise, and even quenching of the magnet. Therefore, a deep understanding of these effects is crucial for the design process. To mitigate the overall coil loss, reasonable structural design and conductor specifications are implemented. Furthermore, through finite-element analysis, the temperature distribution of the magnet under different cooling methods, such as LHe (Liquid Helium) bath and thermal conduction, are calculated in detail. Multiple reasonable cooling structures are also designed to ensure the safety of the magnet.