Large Superconducting Magnet Systems

The increase of energy in accelerators over the past decades has led to the design of superconducting magnets for both accelerators and the associated detectors. The use of Nb-Ti superconducting materials allows an increase in the dipole field by up to 10 T compared with the maximum field of 2 T in a conventional magnet. The field bending of the particles in the detectors and generated by the magnets can also be increased. New materials, such as Nb3Sn and high temperature superconductor (HTS) conductors, can open the way to higher fields, in the range 13-20 T. The latest generations of fusion machines producing hot plasma also use large superconducting magnet systems.Comment: 25 pages, contribution to the CAS-CERN Accelerator School: Superconductivity for Accelerators, Erice, Italy, 24 April - 4 May 2013, edited by R. Baile

Status of the Cold Mass of the Short Straight Section for the LHC

In the framework of the LHC (Large Hadron Collider) R&D program, CERN and CEA-Saclay have collaborated to develop and construct two quadrupole magnet prototypes which have been successfully cold-teste d. This collaboration has been extended as part of French special contribution to the LHC project. The previous design has been adapted to meet the new LHC parameters and two new cold masses are being constructed. This paper describes the new cold masses, their assembly process and the foreseen organization for the industrial production of about 470 units

Construction of the New Prototype of Main Quadrupole Cold Masses for the Arc Short Straight Sections of LHC

Each cold mass of the short straight sections in the eight LHC arcs will contain a 3.25 m long twin aperture quadrupole of a nominal gradient of 223 T/m. This magnet will be aligned in a 5.3 m long inertia tube together with auxiliary magnets on each end. On the quadrupole connection end either a pair of 38 cm long octupole or trim quadrupole magnets will be mounted, on the other end there will be combined sextupole-dipole correctors with a yoke length of 1.26 m. The powering of the main quadrupoles will be assured by two pairs of copper stabilized superconducting bus-bars placed inside the cold mass next to the bus-bars for the main dipole magnets. Each of the two quadrupole apertures will be connected to its quench protection diode. The construction of three prototypes has been entrusted to the CEA/Saclay laboratory, in the frame of the special French contribution to the LHC project. The first cold mass prototype has been completed and warm-measured for its multipole content at CEA. The second cold mass is presently under completion. The paper will review the experience with the development of the quadrupole coils and cold mass construction and gives the results of the first warm magnetic measurements. An outlook for the series manufacture of the 400 arc quadrupole magnets and their cold masses for the LHC machine will complete the report

The short straight sections for the LHC

During more than five years a close collaboration between CERN and CEA-Saclay led to the development and construction of two prototype quadrupole magnets and the integration of one of them into the short straight section of the LHC half-cell test string at CERN. In the frame of the special host country contribution to the LHC project this collaboration has been extended to the CNRS laboratory in Orsay and covers besides the quadrupole magnets the complete cold mass assembly (CEA) and the integration into the short straight section cryostat (CNRS). The short straight sections include not only the main lattice quadrupoles with their protection diodes, they also house different corrector magnets and the beam position monitors. Further, they provide the cryogenic feed units for a half-cell with all the magnet interconnections and the jumper connection to the separate cryo-line. The paper will show the general lay-out of these complex units and elaborate the different aspects of their assembly

The New Superfluid Helium Cryostats for the Short Straight Sections of the CERN Large Hadron Collider (LHC)

The lattice of the CERN Large Hadron Collider (LHC) contains 364 Short Straight Section (SSS) units, one in every 53 m long half-cell. An SSS consists of three major assemblies: the standard cryostat section, the cryogenic service module, and the jumper connection. The standard cryostat section of an SSS contains the twin aperture high-gradient superconducting quadrupole and two pairs of superconducting corrector magnets, operating in pressurized helium II at 1.9 K. Components for isolating cryostat insulation vacuum, and the cryogenic supply lines, have to be foreseen. Special emphasis is given to the design changes of the SSS following adoption of an external cryogenic supply line (QRL). A jumper connection connects the SSS to the QRL, linking all the cryogenic tubes necessary for the local full-cell cooling loop [at every second SSS]. The jumper is connected to one end of the standard cryostat section via the cryogenic service module, which also houses beam diagnostics, current feedthroughs, and instrumentation capillaries. The conceptual design fulfilling the tight requirements of magnet alignment precision and cryogenic performance are described. Construction details, aimed at minimizing costs of series manufacturing and assembly, while ensuring the high quality of this complex accelerator component, are given

Comparison of 2-D Magnetic Designs of Selected Coil Configurations for the Next European Dipole (NED)

The Next European Dipole (NED) activity is developing a high-performance Nb$_{3}$Sn wire (aiming at a non-copper critical current density of 1500 A/mm2 at 4.2 K and 15 T), within the framework of the Coordinated Accelerator Research in Europe (CARE) project. This activity is expected to lead to the fabrication of a large aperture, high field dipole magnet. In preparation for this phase, a Working Group on Magnet Design and Optimization (MDO) has been established to propose an optimal design. Other parallel Work Packages are concentrating on relevant topics, such as quench propagation simulation, innovative insulation techniques, and heat transfer measurements. In a first stage, the MDO Working Group has selected a number of coil configurations to be studied, together with salient parameters and features to be considered during the evaluation: the field quality, the superconductor efficiency, the conductor peak field, the stored magnetic energy, the Lorentz Forces and the fabrication difficulties. 2-D magnetic calculations have been performed, and the results of this comparison between the different topologies are presented in this paper. The 2-D mechanical computations are ongoing and the final stage will be 3-D magnetic and mechanical studies