Normal zone propagation and quench characteristics of Nb3Sn wires with jelly-roll and in-situ processed CuNb reinforcements

The stability of three types of CuNb reinforced Nb3Sn wires has been experimentally studied in order to clarify effects of critical current density, J(c), and Nb fraction in CuNb reinforcements, The stabilities, i.e., minimum quench energy, MQE, and normal zone propagation velocity, v(p), were evaluated for sample wires having low J(c) and low Nb fraction (A) and high J(c) and low Nh fraction (B) with In-situ processed CuNb reinforcement and high J(c) and high Nb fraction with jelly-roll processed CuNb reinforcement (C). The MQE decreased with increase in transport current density normalized by J(c), critical generation density, and Nb fraction, on the other hand, v(p) increased with increasing the transport current density, regardless of Nb fraction. We obtained basic data for the design of magnets having both a high stability and mechanical strength.