Abstract-New polyimide cable insulation schemes improving the cooling of Nb-Ti superconducting coils were recently developed to face the severe heat loads at which the next generation of superconducting accelerator magnets will work.In order to qualify the new insulation, a test campaign was realized to assess both its electrical and mechanical features with respect to the standard LHC insulation. The electrical tests assessed the dielectric strength and inter-turn leakage current to be satisfactory. The mechanical tests investigated the insulation thickness under load and the stress relaxation at ambient temperature, thus providing essential information for the magnetic and mechanical design of the final focusing magnets for the LHC upgrade phase I.Index Terms-LHC upgrade, mechanical and electrical tests, stress relaxation, superconducting magnets cable insulation.

The Short Model Coil (SMC) assembly has been designed, as test bench for short racetrack coils wound with Nb 3 Sn cable. The mechanical structure comprises an iron yoke surrounded by a 20 mm thick aluminium alloy shell, and includes four loading pads that transmit the required pre-compression from the outer shell into the two coils. The outer shell is pre-tensioned with mechanical keys that are inserted with the help of pressurized bladders and two 30 mm diameter aluminium alloy rods provide the axial loading to the coil ends. The outer shell, the axial rods, and the coils are instrumented with strain gauges, which allow precise monitoring of the loading conditions during the assembly and at cryogenic temperature during the magnet test. Two SMC assemblies have been completed and cold tested in the frame of a European collaboration between CEA (FR), CERN and STFC (UK) and with the technical support from LBNL (US). This paper describes the main features of the SMC assembly, the experience from the dummy assemblies, the fabrication of the coils, and discusses the test results of the cold tests showing a peak field of 12.5 T at 1.9 K after training.

Abstract-The Short Model Coil (SMC) working group was set in February 2007 within the Next European Dipole (NED) program, in order to develop a short-scale model of a Nb 3 Sn dipole magnet. The SMC group comprises four laboratories: CERN/TE-MSC group (CH), CEA/IRFU (FR), RAL (UK) and LBNL (US). The SMC magnet was originally conceived to reach a peak field of about 13 T on conductor, using a 2500 A/mm 2 Powder-In-Tube (PIT) strand. The aim of this magnet device is to study the degradation of the magnetic properties of the Nb 3 Sn cable, by applying different level of pre-stress. To fully satisfy this purpose, a versatile and easy-to-assemble structure has to be realized. The design of the SMC magnet has been developed from an existing dipole magnet, the SD01, designed, built and tested at LBNL with support from CEA. In this paper we will describe the mechanical optimization of the dipole, starting from a conceptual configuration based on a former magnetic analysis. Two and three-dimensional Finite Element Method (FEM) models have been implemented in ANSYS and in CAST3M, aiming at setting the mechanical parameters of the dipole magnet structure, thus fulfilling the design constraints imposed by the materials.Index Terms-High field magnets, mechanical modeling, superconducting magnet design.

Abstract-At present Nb 3 Sn Rutherford Cables seem to be the most suitable conductors for next generation superconducting accelerator magnets. These magnets will have a peak field in the coils larger than 10 T and the large Lorentz forces will impose coil pre-stresses significantly larger than 100 MPa. Since Nb 3 Sn is strongly sensitive to strain it is mandatory to characterize the cable under a transverse pressure comparable to the one experienced in future magnets. As a part of its High Field Magnet program, CERN is developing a sample holder for the FRESCA Facility that allows testing 10 mm wide superconducting Rutherford cables under a transverse pressure up to 200 MPa. The sample holder will be able to house cables up to 20 mm wide. In this paper the conceptual design is presented together with the experimental results of the mechanical test performed on a 40 cm long model. The results show that the structure can apply a transverse pressure larger than 200 MPa on 10 mm wide cables with sufficiently high pressure homogeneity.

Abstract-Thecable, by applying different levels of pre-stress. To fully satisfy this purpose, a versatile and easy-to-assemble structure has been realized. The design of the SMC magnet has been developed from an existing dipole magnet, the SD01, designed, built and tested at LBNL with support from CEA. The goal of the magnetic design presented in this paper is to match the high field region with the high stress region, located along the dipole straight section. For this purpose, three-dimensional nonlinear parametric models have been implemented using three codes (CAST3M, ANSYS, and OPERA). This optimization process has been an opportunity to cross-check the codes. The results of this benchmarking are presented here, along with the final design which incorporates the use of end spacers and a surrounding iron structure to deliver a nominal field of 13 T uniformly distributed along the cable straight section.