Quench protection analysis in accelerator magnets, a review of the tools

As accelerator magnets see the increase of their magnetic field and stored energy, quench protection becomes a critical part of the magnet design. Due to the complexity of the quench phenomenon interweaving magnetic, electrical and thermal analysis, the use of numerical codes is a key component of the process. In that respect, we propose here a review of several tools commonly used in the magnet design community.Comment: 4 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Nb-Ti Symmetric Triplets for the LHC luminosity Upgrade

We study a Nb-Ti lay-out for the triplet in the low-beta interaction regions of the Large Hadron Collider, based on a stretched version of the present baseline. The triplet length is increased from the present value of 32 m up to about 60 m. The quadrupoles are based on a two layer coil made with the LHC main dipole cable. A parametric analysis of the dependence of the optics and magnet performances on the triplet length and aperture is carried out

Quench limits in the next generation of magnets

Several projects around the planet aim at building a new generation of superconducting magnets for particle accelerators, relying on Nb3Sn conductor, with peak fields in the range of 10-15 T. In this paper we give an overview of the main challenges for protecting this new generation of magnets. The cases of isolated short magnets, in which the energy can be extracted on an external dump resistor, and chain of long magnets, which have to absorb their stored energy and have to rely on quench heaters, are discussed. We show that this new generation of magnets can pose special challenges, related to both the large current density and to the energy densities.Comment: 7 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet, Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva, Switzerlan

Magnetic Design of Superconducting Magnets

In this paper we discuss the main principles of magnetic design for superconducting magnets (dipoles and quadrupoles) for particle accelerators. We give approximated equations that govern the relation between the field/gradient, the current density, the type of superconductor (Nb-Ti or Nb3Sn), the thickness of the coil, and the fraction of stabilizer. We also state the main principle controlling the field quality optimization, and discuss the role of iron. A few examples are given to show the application of the equations and their validity limits.Comment: 24 pages, contribution to the CAS-CERN Accelerator School: Superconductivity for Accelerators, Erice, Italy, 24 April - 4 May 2013, edited by R. Baile

Conceptual design of 20 T dipoles for high-energy LHC

Availability of 20 T operational field dipole magnets would open the way for a 16.5 TeV beam energy accelerator in the LHC tunnel. Here we discuss the main issues related to the magnet design of this extremely challenging dipole: main constraints, superconductor choice, coil lay-out, iron, forces and stresses, and field quality. A tentative cost estimate is also given. The present technology, based on Nb-Ti and now near to be extended to Nb3Sn superconductor, would allow reaching 15 T operational field. To reach 20 T, HTS conductors capable to carry 400 A/mm2 at 15-20 T under transverse stress of 150-200 MPa are an essential element.Comment: 7 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow Report CERN-2011-003, pp. 13-1

Identification of Assembly Faults through the Detection of Magnetic Field Anomalies in the Production of the LHC Dipoles

Magnetic measurements at room temperature have been used to monitor the production of the superconducting coils of the Large Hadron Collider main dipoles. They have made it possible to identify several assembly errors, e.g. cases of bad gluing of the coil layers, bad conductor positioning, missing pole shims and other problems related to faulty procedures. This paper reviews the experience accumulated so far considering almost 1000 dipoles. After a short outline of the method used to pin out field anomalies and deduce realistic deformation of the coil, an exhaustive list of the cases met during the production is given. A discussion follows on the findings after decollaring as compared to the predictions, including the still open cases

Electromagnetic Design of Superconducting Quadrupoles

We study how the critical gradient depends on the coil lay-out in a superconducting quadrupole for particle accelerators. We show that the results relative to a simple sector coil are well representative of the coil lay-outs that have been used to build several quadrupoles in the past 30 years. Using a semi-analytical approach we derive a formula that gives that critical gradient as a function of the coil cross-sectional area, of the magnet aperture, and of the superconducting cable parameters. This formula is used to evaluate the efficiency of several types of coil lay-outs (shell, racetrack, block, open mid-plane)

Scaling laws for Beta* in the LHC interaction regions

A lay-out for the triplet in the low-beta interaction regions of the Large Hadron Collider based on the present baseline is studied. A parametric analysis of the dependence of the beta function in the interaction point and in the triplet on the magnet length and technology (Nb-Ti or Nb$_{3}$Sn) is carried out. Solutions with large aperture quadrupoles and low beta functions in the interaction point are presented. A final comparison of the triplet lay-outs using different technologies and distance to the interaction point are discussed

The Development of Superconducting Magnets for Use in Particle Accelerators: From the Tevatron to the LHC

Superconducting magnets have played a key role in advancing the energy reach of proton synchrotrons and enabling them to play a major role in defining the Standard Model. The problems encountered and solved at the Tevatron are described and used as an introduction to the many challenges posed by the use of this technology. The LHC is being prepared to answer the many questions beyond the Standard Model and in itself is at the cutting edge of technology. A description of its magnets and their properties is given to illustrate the advances that have been made in the use of superconducting magnets over the past 30 years