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In the family of the High-Luminosity LHC high order correctors, the skew quadrupole was the most critical magnet as three assemblies with different solutions were needed to meet the design specifications. This paper summarizes the prototyping phase of the magnet, discussing the observed nonconformities, the subsequent root cause analyses, and the adopted solutions. A first-hand experience showed us the importance of adopting rigorous quality assurance methods for the electrical insulation, aimed at the early defect detection, and implementing a consistent measurement-to-simulations chain for the optimization of the coils mechanical support. The improvements discussed in the paper are integrated into the final magnet design for the series production of six skew quadrupole correctors.

INFN is developing at LASA laboratory (Milano, Italy) the prototypes of five high order corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions of the High Luminosity-LHC (HL-LHC). These magnets are based on a superferric design, which allows a relatively simple, modular and easy to construct magnet. This activity takes place within the framework of a collaboration agreement between CERN and INFN. Four prototypes, from sextupole to dodecapole, have been built and tested starting in 2016. We present here the last prototype of the high order correctors, to be installed in LHC, the skew quadrupole: magnetic and mechanical design are discussed together with quench protection. We report also on the overall experience gained during construction aiming toward the series production. The power test of the quadrupole, including the training, the qualification and the quench behavior in operational conditions are also described.

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.

INFN is developing at the LASA lab (Milano, Italy) the High Order (HO) corrector magnets for the High Luminosity-LHC (HL-LHC) project, which will equip the interaction regions. Five prototypes, from skew quadrupole to dodecapole, have been designed and tested at LASA. All the HO correctors are based on a superferric design, which allows a relatively simple, modular, and easy to construct magnet. This modularity has been exploited for an engineering change request. The tradeoff between safe handling, force management during cooldown, powering and protection of the magnet is explained in detail. The design of the coils and the mechanical assembly have been improved to increase the efficiency of the series production. Most of the optimizations are aimed to guarantee both a good integration in the LHC framework (i.e., radiation hardness, easiness of installation, safe operation over years), and compatibility with the series production (i.e., standardization of procedures and components for different magnets, reduction of the number of components, standardization of the quality control systems and acceptance tests). All of the produced magnets will be tested at LASA and then delivered to CERN. The design of the test-bed and the optimization of cryogenic and testing procedures is also described in this paper. Following the completion of the prototyping phase, we report in detail the solutions chosen for the HO correctors and we give a perspective of the series construction in industry and acceptance tests at LASA.

The National Institute for Nuclear Physics (INFN) is developing at the Laboratory of Accelerators and Applied Superconductivity (LASA) laboratory (Milano, Italy) the prototypes of five corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions of the High Luminosity Large Hadron Collider (HL-LHC). These magnets are based on a superferric design, which allows a relatively simple, compact, and easy to construct magnet. This activity takes place within the framework of a collaboration agreement between European Organization for Nuclear Research (CERN) and INFN. The first prototypes, a sextupole and an octupole, have been tested in 2016 and 2017, respectively. We present here the results of the cold tests of the decapole that has been assembled and tested in the second half of 2017, including the training performed at 4.2 K and the qualification at 2.17 K. We report also on the overall experience gained during construction and tests and the improvements toward the series production. Other important results concern quench studies.

INFN is developing at LASA Laboratory (Milano, Italy) the prototypes of five corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions (IRs) of the High Luminosity-LHC (HL-LHC). These magnets are based on a superferric design, to allow a relatively simple, modular, and easy to construct magnet. This program takes place within the framework of a collaboration agreement between CERN and INFN. In this paper, we present an overview of the activity, from the design, to the construction and test at the operation condition.

INFN is developing at LASA lab (INFN Milano, Italy) the prototypes of five corrector magnets, from skew quadrupole to dodecapole, which will equip the high-luminosity interaction regions of the High Luminosity-LHC. These magnets are based on a superferric design, which allows a relatively simple, modular, and easy to construct magnet. This activity takes place within the framework of a collaboration agreement between CERN and INFN. The first prototype, a sextupole, has been assembled in early 2016. We present here the results of the cold test, including the training performed at 4.2 K and the qualification at 2.2 K. We report also on the overall experience gained during its construction and test. An important aspect is represented by the analysis of the manufacturing tolerances of the mechanical pieces and the alignment accuracy achieved. These results will serve as a basis for the design of the next magnets, the octupole, and the decapole. Other important results concern the cold performance of the coil-to-coil electrical joints (especially critical in a magnet with a large number of coils), dynamic inductance measurements and quench studies.

The National Institute for Nuclear Physics (INFN) is developing, within the framework of a collaboration agreement with the European Organization for Nuclear Research (CERN), prototypes of five corrector magnets, from skew quadrupoles to dodecapoles, which will equip the high-luminosity interaction regions of the high-luminosity Large Hadron Collider. These magnets are based on a superferric design, which allows a relatively simple, modular, and easy-to-construct magnet. In this paper, we review the main features of the corrector magnets, and we present the results of the manufacture of the sextupole superconducting coils, from the development of suitable solutions for the winding and impregnation to the quality assessment on the series coils, including the results of the first cryogenic tests on a single coil.

CERN and INFN, Italy, have signed an agreement for RD the fringe field analysis; the magnet powering and quench protection; mechanical and construction main choices.