The upgrade of the large hadron collider to achieve higher luminosity requires the installation of twenty-four 150 mm aperture, 12 T, Nb 3 Sn quadrupole magnets close to the two interaction regions ...at ATLAS and CMS. The protection of these high-field magnets after a quench is particularly challenging due to the high stored energy density, which calls for a fast, effective, and reliable protection system. Three design options for the quench protection system of the inner triplet circuit are analyzed, including quench heaters attached to the coil's outer and inner layer, Coupling-Loss Induced Quench (CLIQ), and combinations of those. The discharge of the magnet circuit and the electromagnetic and thermal transients occurring in the coils are simulated by means of the TALES and LEDET programs. The sensitivity to strand parameters and the effects of several failure cases on the coil's hot-spot temperature and peak voltages to ground are assessed. A protection system based only on quench heaters attached to the outer layer can barely maintain the hot-spot temperature below the target limit and cannot guarantee the coil protection under failure scenarios. On the contrary, systems including either inner quench heaters or CLIQ are adequate to protect the coil under all realistic operation and failure scenarios. In particular, the option including outer quench heaters and CLIQ achieves lowest hot-spot temperatures, and highest redundancy and robustness.
In this paper, we describe a general formalism that allows to reduce the spatial dimension of a field problem from 3-D to (2 +1)-D. Subsequently, we identify conditions under which the third ...dimension can be eliminated. We see that the resulting 2-D field problems only decouple if an orthogonality criterion is fulfilled. The approach is based solely on differential-form calculus and can therefore be easily transferred into a discrete setting. As a numerical example, we compute the field of twisted wires.
Purpose - To introduce a Whitney-element based coupling of the Finite Element Method (FEM) and the Boundary Element Method (BEM); to discuss the algebraic properties of the resulting system and ...propose solver strategies.Design methodology approach - The FEM is interpreted in the framework of the theory of discrete electromagnetism (DEM). The BEM formulation is given in a DEM-compatible notation. This allows for a physical interpretation of the algebraic properties of the resulting BEM-FEM system matrix. To these ends we give a concise introduction to the mathematical concepts of DEM.Findings - Although the BEM-FEM system matrix is not symmetric, its kernel is equivalent to the kernel of its transpose. This surprising finding allows for the use of two solution techniques: regularization or an adapted GMRES solver.Research limitations implications - The programming of the proposed techniques is a work in progress. The numerical results to support the presented theory are limited to a small number of test cases.Practical implications - The paper will help to improve the understanding of the topological and geometrical implications in the algebraic structure of the BEM-FEM coupling.Originality value - Several original concepts are presented: a new interpretation of the FEM boundary term leads to an intuitive understanding of the coupling of BEM and FEM. The adapted GMRES solver allows for an accurate solution of a singular, unsymetric system with a right-hand side that is not in the image of the matrix. The issue of a grid-transfer matrix is briefly mentioned.
The magnetization of the superconductor is one of the most important parameters determining the field quality of accelerator magnets. A fast method to quantify the magnetization effect in an entire ...magnet was developed at CERN based on a voltage-current measurement during a powering cycle. The collective magnetization includes the effect due to hysteresis losses in the magnet superconducting filaments, coupling losses in the magnet conductor, and magnetization of the iron yoke. It is calculated by means of an energy balance between the work done by the power converter and the change of magnetic energy in the system. Also, the energy dissipated at any time is calculated. In the magnet test facility at CERN, LHC dipole magnets have been cycled between ±600 A with a ramp-rate of 10 A/s. The magnetization curves deduced from these measurements show a good precision and high reproducibility, mainly due to the high precision of the power converter and the current measurement system. The results have been compared with numerical simulations performed with the computer code ROXIE. The proposed test method can be applied to any type of magnet, is rather easy and fast, and is therefore interesting for checking the reproducibility of the magnetization among a series production of magnets.
FNAL and CERN are developing a twin-aperture 11-T Nb 3 Sn dipole suitable for installation in the LHC. This paper describes the design and parameters of the 11-T dipole developed at FNAL for the LHC ...upgrades in both single-aperture and twin-aperture configurations, and presents details of the constructed dipole models. Results of studies of magnet quench performance, quench protection, and magnetic measurements performed using short 1-m-long coils in the dipole mirror and single-aperture configurations are reported and discussed.
Fermilab and CERN have a joint R&D program with the goal of building a 5.5-m-long twin-aperture Nb 3 Sn dipole magnet suitable for installation in the Large Hadron Collider. The first step of this ...program is the development of a 2-m-long single-aperture demonstration dipole with the nominal field of 11 T at the Large Hadron Collider nominal current of 11.85 kA, 60 mm bore and ~ 20% margin. Prior to the construction of the real magnets, a shorter section of the magnet straight part was assembled to validate the results of the structural finite element analysis and to gain experience with magnet assembly. This paper summarizes the lessons learned from this mechanical model.
Fermilab and CERN have a joint R&D program with the goal of building a 5.5-m-long twin-aperture Formula Omitted dipole magnet suitable for installation in the Large Hadron Collider. The first step of ...this program is the development of a 2-m-long single-aperture demonstration dipole with the nominal field of 11 T at the Large Hadron Collider nominal current of 11.85 kA, 60 mm bore and Formula Omitted20% margin. Prior to the construction of the real magnets, a shorter section of the magnet straight part was assembled to validate the results of the structural finite element analysis and to gain experience with magnet assembly. This paper summarizes the lessons learned from this mechanical model.
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