Residual strain in the Nb$_3$Sn 11 T dipole magnet coils for HL-LHC

Nb$_{3}$Sn magnets are presently built for the HL-LHC accelerator upgrade and are developed for the Future Circular Collider study. The knowledge of the Nb$_{3}$Sn strain state distribution in these magnets is required in order to predict their ultimate performance limit. We have measured the Nb$_{3}$Sn residual strain distribution in an 11 T dipole accelerator magnet coil. Ambient temperature Nb$_{3}$Sn strain maps across 11 T dipole coil cross sections were acquired by means of fast high energy synchrotron x-ray diffraction. Using complementary neutron diffraction measurements the Nb$_{3}$Sn residual strain and stress was measured in the four largest conductor blocks of a massive 11 T dipole coil segment.