Laser-Induced Quench Study of the Magneto-Thermal Stability of Nb3Sn Wires

In the pursuit of developing 14+ T Nb3Sn magnets for a future energy-frontier circular collider, there is a growing demand for wires with enhanced critical current density (J(c)), larger diameters, and lower copper-to-non-copper ratios. These requirements pose significant challenges to maintaining magnetothermal stability of the superconducting wires. This paper explores the technical aspects of non-traditional measurements of the Minimum Quench Energy (MQE) triggered by an ultra-violet pulsed laser. The advantage of a pulsed laser as opposed to the more commonly used resistive heaters is the speed: the laser deposits the energy in nanoseconds, significantly faster than the characteristic time of temperature diffusion in the samples tested. Methods for calibration of the energy absorbed by the wire are also discussed. The stability of internal tin and powder-in-tube Nb3Sn wire designs, originally specified for the requirements of the quadrupole (MQXF) magnets for the High Luminosity upgrade of the Large Hadron Collider, was evaluated under applied magnetic fields ranging from 5 T to 15 T and at both 1.9 K and 4.2 K. Notable trends were observed in the energy required to induce a quench at a constant current level as a function of the magnetic field. These trends persisted even as the superconductor approached current levels where premature quenches occur. Results suggest that the superconductor applied in the MQXF magnets cannot be quenched at the operating point by the energy available in this study, with a considerable margin.