Stability study of Bi‐2212 conductor based on perturbation spectrum for hybrid superconducting magnet

A hybrid superconducting central solenoid employs Bi‐2212 high‐temperature superconductors and Nb3Sn low‐temperature superconductors under the design of the Institute of Plasma Physics, Chinese Academy Of Science for further upgrade to CFETR, namely, the China Fusion Engineering Testing Reactor. The conductor type of both parts is cable‐in‐conduit conductors. This paper mainly focuses on stability study of the inner high‐temperature superconductors part whose conductor works under a peak magnetic field of 16.79 T, and the maximum operating current of each turn is 50 kA. The simulation based on a 1‐D simplified model is performed using the code THEA (thermal hydraulic and electric analysis of superconducting cable). Firstly, a brief analysis of stability considering the AC loss during current ramp‐up is studied. Then, the stability margins in cases of different perturbations with varied lengths and durations are calculated, and a qualitative explanation of the result is proposed. Besides, the inlet pressure and pressure drop crucially influence the convection heat transfer between strands and helium; thus, the effect of these two factors on stability margin is discussed. All these results will provide important references for further optimization of this hybrid magnet. Copyright © 2017 John Wiley & Sons, Ltd.