Design and test of a model superconducting correction winding around a grooved vacuum chamber [of LHC]

In the framework of research for the Large Hadron Collider (LHC), it has been envisaged to install distributed correction windings around the vacuum chamber inside the 50 mm bores of the 10 m long twin-aperture dipoles. At a distance of 10 mm from the center, the field homogeneity of the main dipoles may lead to systematic relative errors of up to 5×10^-4 due to the sextupolar component and 1×10 ^-4 due to higher multipoles. These errors depend on the operational conditions and need to be dynamically compensated. A design adapted to the LHC accelerator where thousands of correctors are needed has been investigated. It is based on the principle of minimizing the number of operations during manufacture in such a way that no manual operation is needed to adjust the accurate positioning of the coils. A 0.3 m long maquette and a 0.8 m long model of sextupolar correction winding have been manufactured at CERN to check the validity of the method. They both gave satisfactory results; the critical current of the short sample superconducting wire was reached after a few training quenches