Construction and cold test of the superferric dodecapole high order corrector for the LHC High Luminosity upgrade

The High Luminosity LHC (HL-LHC) is a program to upgrade the performance of the collider in order to achieve, in the ATLAS and CMS collision regions, instantaneous luminosities a factor of five larger than the actual nominal value. To obtain this result, all the magnets in the collision region will have to be substituted, together with other important devices. In the framework of this program, the Italian National Institute for Nuclear Physics (INFN-LASA laboratory) is entrusted to develop five corrector magnets (skew quadrupole, sextupole, octupole, decapole, and dodecapole), which in the magnet chain will have to correct the magnetic imperfections of the main magnets in the regions (low-beta quadrupoles Q1/Q3 and dipole D1/D2). These corrector magnets have been designed with relatively simple, robust, and easy to construct concepts, using superferric configuration. The first prototypes, a sextupole, an octupole, and a decapole, have been tested in 2016 and 2017. We present here the prototype of dodecapole. We report magnetic and mechanical designs and the experience during construction. The qualification, the cold test, and the quench behavior in operational conditions are also described.