Quench Propagation in Nb$_3$Sn Rutherford Cables for the Hi-Lumi Quadrupole Magnets

The quadrupole magnets for the LHC High Luminosity (Hi-Lumi) upgrade will be based on Nb_3Sn Rutherford cables that operate at 1.9 K and experience magnetic fields larger than 12 T. Because of the large stored energy, one of the major issues in the design of these magnets is their protection. To study the quench propagation in Nb_3Sn Rutherford cables for the Hi-Lumi Quadrupole magnets, a campaign of measurements was carried out in the FRESCA test station at CERN. In addition to the critical and stability current measurements at 4.3 K and 1.9 K, we performed a series of tests where the quenches were induced by resistive heaters impregnated in the cable. The longitudinal and transversal speeds of the normal zone propagation were investigated at different magnetic fields and operating currents. In this paper, the numerical and experimental results are reported, compared and discussed.