The next generation of high-field magnets for accelerators relies on Nb 3 Sn conductors, mostly Rutherford-type cables. Superconducting cables are anisotropic composites structures that can comprise ...strands, impregnation and insulation wrapping materials. Moreover, Rutherford cables are characterized by a multi-scale architecture going from the micron-size sub-elements to meter-size coils. Due to the mechanical sensitivity of the Nb 3 Sn material, the sub-element behavior drives the performance of the magnet. To predict and improve the performance and behavior of the magnets, numerical modeling is now crucial. The multi-physic and multi-axial loadings, the complex multi-scale structure and the intrinsic properties of the Nb 3 Sn material require three-dimensional models to be able to understand and represent the different phenomena. A tool that is able to generate 3D Finite Element (FE) model of a Rutherford cable has been developed at CEA over the last years in the framework of the CoCaSCOPE approach. It allows generating a meshed FE model from the main cable parameters (size, number of strands, etc.) and usable with multi-physic simulation software. This paper presents the different steps to construct the geometry of the cable, and the main features of the mesh. Techniques to model different configurations are presented, considering the stainless-steel core and/or a keystoned shape. Today, the CoCaSCOPE mesh generator (CoCaSCOPE-MG) is open to the scientific community. The authors propose to generate any type of Rutherford cable on demand.
R2D2, the Research Racetrack Dipole Demonstrator, is a short model being developed within a collaboration between CEA Paris-Saclay and CERN. The goal of the program is to develop key technologies for ...future high field 16 T Nb3Sn magnets for particle colliders. In the particular case of block-coil designs, two different cable grades are wound in the same coil layer, in order to maximize the current density, therefore to minimize the size of the magnet and the use of superconductor. One of the most challenging technologies with this grading concept, is the connection between two cables grades. CEA Paris-Saclay has proposed a concept of external joints, for which the cable exits are guided outside of the coil to perform the connections between the cable grades. The R2D2 project is aimed at demonstrating this technology in a representative demonstrator magnet, while simplifying and reducing the risks when possible, as an intermediate step towards 16 T magnets. In particular, the magnet is composed of single-layer racetrack coils, mainly to reduce the use of conductor and simplify some fabrication steps. However, the complexity inherent to the external joints requires a special focus in the design of the coil ends. To do so, the design of the magnet has been performed using a combination of CAD (Computer Aided Design), magnetic and mechanical 3D FEM (Finite-Elements Models). This paper will explain the design choices leading to a safe operation of the magnet in terms of peak fields and peak stresses.
The design of superconducting magnets for accelerator and detector components dedicated to the future of high energy physics requires detailed analysis of their mechanical behavior, in particular ...under magnetic and/or thermal solicitations. Numerical simulation is more and more used to optimize these components and to improve their performances in constrained environments. In this context, the numerical modeling process may require to operate several computing codes, which involves the implementation of spatial discretization (meshes) that are not always compatible together. This situation raises the problem of data transfer and of possible dispersion of simulation parameters. Moreover, the numerical modeling process is not always formalized, and it can be difficult to iterate in the case of parametric studies. This paper describes the implementation of magneto-mechanical numerical processes into the SALOME open source platform. SALOME is a numerical framework which offers interoperability between Computer-Aided Design (CAD) modeling and Computer-Aided Engineering (CAE) simulation software. It makes the implementation of coupling between computing codes (computation schemes) accessible. This simulation platform also provides a generic and efficient user interface, and is as well fully scriptable in Python language. On the basis of the design of the SMC dipole magnet, the authors will describe the various modules of the platform (geometry, mesh, supervision and visualization), and present the status of the developments in progress. It will be pointed out what can be gained for magnet designers in terms of process formalization and transfer of know-how, and what is the level of complexity for the development of a dedicated software tool.
Hybrid magnets enable to achieve very high magnetic fields by combining resistive insert magnets with a large bore superconducting outer coil. In order to reduce the electromagnetic coupling between ...the coils, we introduce an eddy-current shield between the resistive and superconducting magnet. This additional shield is responsible for heat loads. To limit the degradation of the thermal behavior of the cold mass, an innovative support ferrule has been designed. It allows rigid connection of the eddy-current shield to the magnet structure. In this paper, the worst magnetic failure scenario is identified and modeled. It results in large transient forces applying to the structure. Transient mechanical analysis of the hybrid magnet structure featuring innovative support ferrule is presented. Simulations show that the proposed configuration leads to lower mechanical stresses than a configuration featuring a suspended shield.
The Nb3Sn FRESCA2 dipole magnet is dedicated to upgrade the CERN cable test facility FRESCA. It is also a technological demonstrator of large-aperture Nb3Sn accelerator magnet. It has an aperture of ...100 mm and a target bore magnetic field of 13 T. It is composed of four 1.5-m-long double-pancake "block-type" coils, manufactured following the wind, react and impregnation technique. It is developed by CEA and CERN in the framework of a collaboration agreement, in the continuity of the EuCARD program. Through the fabrication of two full-scale copper prototypes, the different steps of the coil fabrication process (winding, heat treatment, splicing, instrumentation, impregnation, and transport) and the corresponding tooling have been adjusted. The final winding and reaction procedure integrates the possibility to open longitudinal gaps in the winding table and in the central post, in order to accommodate partially the longitudinal contraction of the cable during reaction. This new feature has been experienced through full-scale tests using superconducting cable with a reduced number of turns. This paper reports on the fabrication procedure of these coils. The production phase of the superconducting magnets has started in June 2015.
Based on a close collaboration between CEA and CNRS, a new hybrid magnet is being built at LNCMI-Grenoble. By combining a resistive insert, which is made of Bitter and polyhelix coils, with a large ...bore superconducting outsert, an overall continuous magnetic field of at least 43 T will be produced in a 34-mm warm bore aperture. The superconducting coil relies on the novel development of a Nb-Ti/Cu Rutherford cable-on-conduit conductor cooled down to 1.8 K by a bath of superfluid helium at atmospheric pressure and will produce a nominal magnetic field of 8.5 T in a 1.1-m cold bore diameter. After thorough reviews of the hybrid magnet design, which have anticipated possible upgrades of the maximum magnetic field produced, the project has entered in its production phase. The status and the next steps of the project will be reviewed highlighting the remaining technical challenges.
This paper reports on the design of FRESCA2, a dipole magnet model wound with Nb 3 S n Rutherford cable. This magnet is one of the deliverables of the High Field Magnets work package of the European ...FP7-EuCARD project. The nominal magnetic flux density of 13 Tesla in a 100 mm bore will make it suitable for upgrading the FRESCA cable test facility at CERN. The magnetic layout is based on a block coil, with four layers per pole. The mechanical structure is designed to provide adequate pre-stress, through the use of bladders, keys and an aluminum alloy shrinking cylinder.
A CEA-CNRS French collaboration is currently developing a new hybrid magnet to produce in a first step a continuous magnetic field of 43 T in a 34-mm warm bore aperture. This magnet combines a ...resistive insert, composed of Bitter and polyhelix coils, and a large bore superconducting "outsert." The superconducting coil is based on the novel development of a Nb-Ti/Cu Rutherford Cable On Conduit Conductor (RCOCC) cooled down to 1.8 K by a bath of superfluid helium at atmospheric pressure. It aims at producing a nominal magnetic field of 8.5 T in a 1.1-m cold bore diameter. The specifications of the RCOCC will be presented together with the design and parameters of the cryogenic system. The solution to reduce the coupling between resistive and superconducting coils will be recalled as well as the constraints for designing the mechanical structure. The design study phase is coming to an end. The status of the conductor production and the next steps of the project are presented.
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