Analysis on thermal stability of Rutherford cable fabricated by quasi-isotropic strands

A preliminary design of a Rutherford cable (Rfc) consisting of a copper core and 10 Quasi-isotropic Strands (Q-ISs) with symmetrical geometry is proposed. The current sharing temperature (T_cs), minimum quench energy (MQE), and normal zone propagation velocity (NZPV) are significant for determining the thermal stability performance of the superconducting cable. Firstly, an electric model of the conductor equivalent circuit is established, and the algebraic equations are derived. The model is validated with the empirical formula by calculating the T_cs of a single Q-IS. Using the validated model, the T_cs of Rfc fabricated by Q-ISs operating in liquid helium temperature at different magnetic fields are obtained. Then, to quantitatively characterize the effect of Q-ISs located at different positions on Rfc after a heating disturbance, the MQE and NZPV of Rfc are numerically simulated by the finite element method, which uses a 3-D thermal model with a homogenization procedure and coupled with the previous electrical model. The analyzed results provide a preliminary assessment of the thermal stability of the high-current superconducting cable and provide important guidance for subsequent experiments and prospective engineering applications.