Field Quality Measurements in a Single-Aperture 11 T $\hbox {Nb}_{3}\hbox {Sn}$ Demonstrator Dipole for LHC Upgrades

The upgrade of the Large Hadron Collider (LHC) collimation system foresees additional collimators in the LHC dispersion suppressor areas. The longitudinal space for the collimators could be provided by replacing some NbTi LHC main dipoles with shorter 11 T Nb₃Sn dipoles. To demonstrate this possibility, Fermilab and CERN have started a joint program to develop a Nb₃Sn dipole prototype suitable for installation in the LHC. The first step of this program is the development of a 2-m-long, 60-mm-bore, single-aperture demonstrator dipole with the nominal field of 11 T at the LHC operational current of 11.85 kA. This paper presents the results of magnetic measurements of the single-aperture Nb₃Sn demonstrator dipole including geometrical harmonics, coil magnetization, and iron saturation effects. The experimental data are compared with the magnetic calculations.