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The Falcon Dipole (Future Accelerator post-LHC Cos-theta Optimized $\rm {Nb_3Sn}$ Dipole) is a single aperture $\rm {Nb_3Sn}$ cos-theta dipole short model in the framework of the Future Circular Collider (FCC) project. The Italian Institute of Nuclear Physics (INFN), in collaboration with CERN, is in charge of designing and constructing the magnet, which is a crucial step towards the construction of High Field $\rm {Nb_3Sn}$ magnets suitable for a post LHC collider. This paper recalls the electromagnetic design, the field quality and performances of the Falcon Dipole. The coil ends design has been implemented in a 3D FEM to study the peak field distribution on the magnet and influence on field quality. A special focus is given to the 2D analysis to study the effect of superconductor magnetization on field quality from the injection to the final energy and then to investigate the effectiveness of compensation methods.

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 LASA Laboratory (INFN, Milan, Italy) is developing an unconventional type of superferric magnets suitable to arbitrary multipole order, which we refer to as round coil superferric magnets. This type of magnet is suitable for strain-sensitive superconductors because it uses round coils with large bending radius to create the magnetic field, while the round yoke with arbitrary multipoles is able to create the desired harmonic component for the magnet. The electromagnetic design of such magnet in sextupole configuration has been already presented. In this paper, we present the progresses in the construction of the prototype, the results of the test of the first coil produced at LASA with the MgB 2 conductor, and the detailed design of the mechanical structure. This activity is part of a collaboration between INFN and CERN in the high luminosity LHC program.

The EuroCirCol project is part of the Future Circular Collider (FCC) study under the European Union leadership in the framework of a H2020 project. In particular, the Italian Institute for Nuclear Physics, in collaboration with CERN and other European laboratories, is developing the design of a cos theta ${{\rm Nb}_{3}{\rm Sn}}$ dipole magnet which will be part of the Conceptual Design Report of the FCC studies in 2019. The magnet, with an aperture diameter of 50 mm and a bore field of 16 T, will be able to bend the beams at final energies and within collider size constraints. Here we present an update of the electromagnetic design of the ${{\rm Nb}_{3}{\rm Sn}}$ cos theta dipole in double-aperture configuration, the 2-D mechanical analysis, and also the 3-D coil-ends study.

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.

The National Institute for Nuclear Physics (INFN) is developing, at the Laboratory of Accelerators and Applied Superconductivity (LASA Milan, Italy), five families of corrector magnets, from skew quadrupole up to dodecapole order, which will be installed in the interaction regions of the High-Luminosity Large Hadron Collider (LHC). These magnets are based on a superferric design, which allows a relatively simple, compact and easy-to-construct magnets. This activity takes place within the framework of a collaboration agreement between CERN and INFN. The magnets have been designed and prototype units have been built and tested for the sextupole, octupole, and decapole orders. Magnetic measurements have been performed in order to characterize the field quality, and to validate the design and construction. This paper presents the instruments and the approach for the magnetic measurements on the prototype magnets. Moreover, the results of measurements at cryogenic temperature, up to the nominal field level, are reported. The magnetic field quality, in terms of transfer function and field multipoles, is analysed as function of the excitation level. The iron saturation effects, which are a major concern of the selected design, are compared with the 3-D magnetic calculations and discussed in view of the construction of the series magnets to be integrated in the corrector package assembly.

The next generation particle accelerators will need to increase by an order of magnitude the center-of-mass energy: a viable solution is a 100 TeV circular collider, temporarily called Future Circular Collider (FCC). To achieve this goal, a new generation of double aperture superconducting magnets, capable of generating a high quality, stable 16 T magnetic field in a 50 mm bore is being developed. In order to achieve this challenging task, the CERN's plan includes several intermediate steps in the development of accelerator-grade Nb3Sn magnets. The first constructive phase will be a 1.5 m long, single aperture cos-theta dipole, with a target central magnetic field of 12 T and an ultimate field of 14 T. In this contribution, the preliminary 2D design of this short model, named Falcon Dipole (Future Accelerator post-Lhc Cos $\theta$ Optimized Nb $_3$ Sn Dipole) will be presented in detail. It features a 2-layers design, with Nb3Sn state-of-art conductor in order to generate the required field. A solution for the mechanical design will also be presented: the necessary pre-stress will be given by a shell-based concept using bladders and keys. This technique avoids giving all the pre-load with just the collaring and it allows to obtain about half of the pre-stress during the assembly of the magnet at room temperature, and full pre-stress in second instance thanks to the cool down. The FalconD project aims at gaining experience on the technology involved to reach fields above 11 T with Nb3Sn coils.

The High Luminosity Large Hadron Collider (HL-LHC) is the new flagship project of CERN. First endorsed in 2013 and approved in 2016, HL-LHC is an upgrade of the accelerator aiming to increase by a factor of ten the statistics of the LHC collisions at the horizon of 2035–2040. HL-LHC relies on cutting edge technologies: among them, large aperture superconducting magnets will replace the present hardware to allow a smaller beam size in two interaction points (IPs). The project involves the construction of about 150 magnets of six different types: the quadrupole triplet, two main dipoles and three orbit correctors. The triplet, manufactured at CERN and in the USA, will consist of 30 magnets based on Nb3Sn technology, with an operational peak field of 11.4 T. These will be the first quadrupole Nb3Sn magnets installed in a particle accelerator. The other five types of magnets, all relying on Nb–Ti technology, present non-trivial challenges in the design and construction; they will be manufactured as part of in-kind contribution under the responsibility of institutes in Japan, China, Spain, and Italy. The project is now in the phase of transition between qualification through short models and prototypes and the beginning of the series construction. In this paper we review the magnet requirements, the reasons for selecting the design, the technological challenges with respect to previous projects, and we summarize the steps that have been taken to validate the baseline.

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 Italian Institute for Nuclear Physics (INFN), in collaboration with CERN, is going to build the short model in Nb $_3$ Sn of the main bending dipole for the hadron-hadron Future Circular Collider (hh-FCC). The magnet will be developed on the basis of the baseline design presented in the FCC Conceptual Design Report (CDR) in the end of 2018. In particular, it will be based on cosine-theta design, with an internal aperture diameter of 50 mm and a Bladder & Key configuration for the mechanics. The main purpose of the model construction is to demonstrate the feasibility of a magnet dipole with field quality characteristic suitable for a collider and magnetic field above the LHC frontier.The mechanical structure, which is a critical aspect of the magnet design, especially for the brittleness of the Nb $_3$ Sn cables, will have to demonstrate the effectiveness to reach the highest performance achievable in terms of bore magnetic field. Here we present both the electromagnetic and mechanical design study of the model.

The LASA Laboratory (INFN, Milan) is working in the High Luminosity LHC program to develop, in collaboration with CERN, six different types of High Order corrector magnets. In this framework, in parallel with a conventional design of superferric magnets with LTS conductor, the LASA is focusing on the research of new superconducting materials which may have applications in particle accelerator magnets. To this purpose, LASA is developing a new type of superferric magnet suitable to arbitrary multipole order, called Round Coil Superferric Magnets (RCSM). The iron yoke shaped with an arbitrary number of poles is able to create the desired harmonic component using only one single round coil with a large bending radius suitable for very strain-sensitive superconductors. The electromagnetic design of a sextupole configuration of the magnet and the production of the first superconducting MgB2 round coil prototype have been already presented. In this paper, we expose the optimization of the iron yoke and polar expansions assembly of the first magnet semi-module prototype. The results of the whole powering test are described in detail and the analysis of the magnetic performances are compared with those of classical superferric correctors.

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.

The LASA Laboratory (INFN, Milan) is developing a new type of superferric magnets suitable to arbitrary multipole order, which we refer to as round coil superferric magnets. It is based on the previous proposal of I. F. Malyshev and V. Kashikhin. This type of magnet is suitable for strain-sensitive superconductors because it only uses a single round coil, which has a large bending radius, to create the magnetic field. The round yoke with arbitrary multipoles is able to create the desired harmonic component for the magnet. A preliminary electromagnetic design of such magnet in sextupole configuration was presented, using MgB2 superconducting tape for the coil. In this paper, we present the advances in the study for the construction of the prototype. We analyze the electromagnetic properties of the coil and of the round multipole iron yoke, focusing on the optimization of the main desired multipole harmonic. We also study the mechanics and quench protection, considering a new type of MgB2 superconducting cable for the coils. At the end of 2017, the magnet will be assembled in the LASA laboratories and then tested in 2018.

International audience; A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb$_3$Sn technology, are being pursued in Europe and in the U.S. In these programs, cos-theta, block-type, common-coil, and canted-cos-theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs.

© 2016 IEEE. This paper presents the analysis of some quench tests addressed to study the dynamic effects in the 1-m-long 120-mm-aperture Nb3Sn quadrupole magnet, i.e., HQ02b, designed, fabricated, and tested by the LHC Accelerator Research Program. The magnet has a short sample gradient of 205 T/m at 1.9 K and a peak field of 14.2 T. The test campaign has been performed at CERN in April 2014. In the specific tests, which were dedicated to the measurements of the dynamic inductance of the magnet during the rapid current discharge for a quench, the protection heaters were activated only in some windings, in order to obtain the measure of the resistive and inductive voltages separately. The analysis of the results confirms a very low value of the dynamic inductance at the beginning of the discharge, which later approaches the nominal value. Indications of dynamic inductance variation were already found from the analysis of current decay during quenches in the previous magnets HQ02a and HQ02a2; however, with this dedicated test of HQ02b, a quantitative measurement and assessment has been possible. An analytical model using interfilament coupling current influence for the inductance lowering has been implemented in the quench calculation code QLASA, and the comparison with experimental data is given. The agreement of the model with the experimental results is very good and allows predicting more accurately the critical parameters in quench analysis (MIITs, hot spot temperature) for the MQXF Nb3Sn quadrupoles, which will be installed in the High Luminosity LHC.