Two-dimensional quench simulation of composite CuNb/Nb₃Sn conductors

In order to clarify effect of utilizing a Nb rich CuNb reinforment on superconducting stability, r-z two-dimensional time-dependent numerical simulations on composite CuNb/Nb₃Sn wires are conducted. The time variations of temperature and current density distributions, minimum quench energy (MQE), and normal zone propagation velocity (ν_p) of a Cu-17vol%Nb/Nb₃Sn wire, a Cu-63vol%Nb/Nb₃Sn wire, and a conventional Cu/Nb₃Sn wire are investigated. The increase of the volume fraction of an outermost Cu stabilizer provides high MQE but decreases the total current density. Although the ν_p is not significantly influenced by the Nb fraction, the Nb rich CuNb reinforcement sacrifices the MQE for its high tensile strength. It is important for magnet design to control the volume fraction of the Cu stabilizer and Nb fraction in the CuNb reinforcement to balance the desired current density, tensile strength, and superconducting stability.