Speaker
Description
Proposed 14 T Nb3Sn magnet designs for a future energy-frontier circular collider often call for wires with higher Jc, larger diameter and lower copper to non-copper (Cu:nonCu) ratio. As well as pushing Nb3Sn superconducting wire technology to its performance limits, these characteristics all prove challenging for magneto-thermal stability.
This study investigates the stability of Nb3Sn wires using an unconventional approach to measure the Minimum Quench Energy (MQE), employing an ultra-violet (UV) laser to initiate quenches. The use of a pulsed laser offers an advantage over traditionally used resistive heaters, depositing the energy within nanoseconds – much faster than the characteristic time of temperature diffusion in the samples tested.
Stability has been experimentally studied for a range of internal tin and powder-in-tube Nb3Sn wire designs, comparing samples differing in copper residual resistance ratio (RRR), Cu:nonCu ratios, wire layouts, states (virgin wire compared to strands extracted from cables), and heat treatments. In each case, the MQE has been determined in external applied fields in the range of 6 T – 15 T and at both 1.9 K and 4.2 K. The stability of the tested wires is benchmarked against the well-established Restacked Rod Process (RRP®) wire with 108/127 layout employed in the quadrupole (MQXF) magnets for the High Luminosity upgrade of the Large Hadron Collider (HL-LHC project).
