Test of Optimized 120-mm LARP $\hbox {Nb}_{3}\hbox {Sn}$ Quadrupole Coil Using Magnetic Mirror Structure

The U.S. Large Hadron Collider accelerator research program is developing a new generation of large-aperture high-field quadrupoles based on Nb₃Sn conductor for the high-luminosity upgrade of the Large Hadron Collider. Tests of the first series of 120-mm-aperture high-gradient quadrupole (HQ) coils revealed the necessity for further optimization of the coil design and fabrication process. Modifications in coil design were gradually implemented in two HQ coils previously tested at Fermi National Accelerator Laboratory using a magnetic mirror structure (HQM01 and HQM02). This paper describes the construction and test of an HQ mirror model with a coil of optimized design and with an interlayer resistive core in the conductor. The cable for this coil was made of a smaller diameter strand, providing more room for coil expansion during reaction. The 0.8-mm strand, used in all previous HQ coils, was replaced with a 0.778-mm Nb₃Sn strand of RRP 108/127 subelement design. The coil was instrumented with voltage taps, heaters, and strain gauges to monitor mechanical and thermal properties and quench performance of the coil.