Quench Safety Simulation and Verification of Superconducting Coils for the SC200 Superconducting Cyclotron

The SC200 superconducting cyclotron for hadron therapy is under construction based on an agreement of the Institute of Plasma Physics Chinese Academy of Sciences and the Joint Institute for Nuclear Research in Russia. The cyclotron will provide a 200-MeV proton beam with maximum current of 400 nA. Thanks to the superconducting magnet, the cyclotron is very compact and light. The yoke weight is about 35 tons. The Hefei team took the responsibility to develop this laser-triggered switching magnet in the past two years. Early this year, the magnet was tested with the iron system. The operating current is 140 A. The magnetic energy is about 4 MJ. In order to decrease the quench risk of the switched capacitor coil, an FEM quench model that can perform quench dynamics simulations of the main magnet system is developed. A quench test is performed to verify the safety of the coil. The hotspot temperature is about 60 K, the max voltage is less than 800 V, and the energy extraction time is about 15 s. The magnet system is, therefore, safe during a quench.