Preliminary 3D Mechanical Design of the FCC-hh Main Quadrupoles

International audienceFor the Future Circular Collider hadron-hadron (FCC-hh), a 100 TeV post Large Hadron collider machine, 750 main quadrupoles with a 360 T/m gradient over a magnetic length of 7 m are required. They consist of a double aperture based on a laminated collar structure similar to the LHC MQ technology. In this paper, a preliminary 3D finite element analysis is performed to evaluate the stresses and strains of the complete magnet structure, with particular emphasis on maintaining coil pre-stress at the pole-coil interfaces under operation. Numerical results during preload, cool-down, and energization are presented in detail and discussed. The peak stress is of the order of 160 MPa in the Nb3Sn coil with a localized gap of less than 6 μm at the coil-pole interface under nominal operation. The stress in the mechanical structure is bearable with only high stress values confined to very small areas

EuroCirCol 16 T Block-Coils Dipole Option for the Future Circular Collider

International audienceEuroCirCol is a conceptual design study for a post-LHC research infrastructure based on an energy-frontier 100 TeV circular hadron collider. In the frame of the high field accelerator magnet design work package of this study, three different layouts for double-aperture dipole magnets made of Nb3Sn conductors and providing a field of 16 T in a 50-mm aperture are being considered: block-coils, common-coils, and cosine-theta. All options are being explored and will be compared based on the same assumptions, in particular with regards to conductor performance, operating temperature and margin. This paper details the block-option presently under development at CEA. After an exploratory phase of various block-coils possibilities (cable dimensions, number of layers, cable grading) the design converged to a four layer magnet. An internal grading-two different geometries of cables are used in the coil-driven by a conductor saving is required. An electromagnetic analysis of the magnet cross-section in a 2-in-1 configuration is performed, coupled to a protection investigation. Preliminary results of a mechanical study on a bladder-and-key single aperture magnet are also reported

Exploration of Two Layer Nb3Sn Designs of the Future Circular Collider Main Quadrupoles

The goal of this study is to propose an alternative FCC quadrupole design where the risk from both their fabrication and their operation in the machine is reduced compared to previous analysis. Therefore, the number of coil layers has been reduced from four to two and the load-line margin has been increased from 14% to 20% compared to previous investigations ('Design of a Nb3Sn 400 T/m quadrupole for the future circular collider,' IEEE Trans. Appl. Supercond., vol. 28, no. 3, p. 4004905, Apr. 2018). Indeed, the idea is to only challenge the ∼5000 FCC main dipoles and stay at a relatively low complexity for the ∼700 FCC main quadrupoles so they have a limiting impact on the machine operation and reliability. An exploration of the strand diameter (0.7-0.9 mm), the cable size (40-60 strands), as well as the protection delay (30-40 ms) is performed on two-dimensional (2-D) magnetic designs of the FCC main quadrupole. A discussion on cable windability allows for the selection of one design generating 367 T/m. The design is mechanically constrained with a conventional collar structure leading to collaring peak stress of 115 MPa. A single coupling-loss-induced quench unit ensures a safe magnet operation with a 300 K hotspot temperature.acceptedVersionPeer reviewe

2-D and 3-D Design of the Block-Coil Dipole Option for the Future Circular Collider

International audienceIn the framework of the EuroCirCol project, the development of a conceptual design of the future circular collider main dipole is performed. The status of the block-coil option under investigation at CEA Saclay is presented. First, a two-dimensional (2-D) electromagnetic analysis is performed in a double aperture configuration with an interbeam separation of 250 mm. This is completed by a 3-D magnetic optimization, taking into consideration the analysis of the peak field value and position, as well as the coil ends integrated field quality. The main objective of the 3-D optimization is to keep coil ends as short as possible. The field quality optimization satisfies all requirements and leads to a peak field lower in the ends compared to the straight section. Finally, a 2-D mechanical study relying on a shell-based structure using bladders and keys is carried out. All main loading steps of the coils are taken into account

Mechanical behavior of a 16-T FCC dipole magnet during a quench

International audienceFuture accelerator magnets are pushed to their limits in terms of magnetic field, mechanical strength and from the quench protection point of view. These forces the magnet designers to rethink the quench modelling. One issue that has not so far been largely explored is the mechanical behavior of the superconducting coils during a quench. This can cause limitations to the design of high-field accelerator magnets. This paper focuses on mechanical behavior in the event of a quench of an Nb3Sn 16 T dipole magnet currently developed in the framework of the EuroCirCol project in view of the future circular collider conceptual design study. The thermo-mechanical analysis is performed through the finite element modeling. The analysis takes into account the Lorentz force and the thermal stress due to the nonuniform temperature distribution in the winding during a quench

FCC-hh conceptual designs and windability of the Main Quadrupoles

In the framework of a design study for a post-LHC 100 TeV cir-cular hadron collider, namely FCC-hh, high gradient Nb3Sn lat-tice quadrupoles were investigated, following closely the specifi-cations from the optic layout of that machine. After several iter-ations, a baseline design of the Main Quadrupole (MQ) was se-lected and, then, included in the FCC-hh Conceptual Design Re-port. The paper deals with the preliminary results of the 3D elec-tromagnetic and mechanical conceptual design. The 3D design of Nb3Sn coil ends is known to be a critical phase, especially for small apertures. To tackle the potential issues, 3D electromagnetic design was first carried out, taking into account the field quality constraints, the field margins in critical areas, and the windability of the coil ends. Then, winding trials with actual cables were performed, to help selecting designs and identifying critical geometrical parameters.acceptedVersionPeer reviewe

Manufacturing of the EuCARD2 Roebel-Based Cos-Theta Coils at CEA Saclay

In the framework of the FP7 EuCARD2 project, CEA Saclay developed a cos-theta insert magnet, wound with REBCO high temperature superconductor Roebel cable. Each dipole coil consists of a single arched layer of conductors, insulated with a glass fiber sleeve and impregnated with epoxy resin for mechanical reinforcement. Tooling has been developed to carefully guide the Roebel cable during the winding phase, transfer the coil to the impregnation mold and impregnate it. The magnet is made of two coils assembled around a Nitronic 40 hollow core to mechanically limit its ovalization when operating in a 13 T background field. The structure is completed by the addition of an external stainless steel tube surrounding the coils. This paper details manufacturing tools and fabrication processes validated with stainless steel dummy cable and relates about the fabrication of two superconducting coils. The magnet assembly and preparation for the tests in standalone configuration in INFN-LASA test facility are foreseen for the end of this year