Search

Superconducting magnets can exhibit training quenches during successive powering to reaching nominal performance. The slip–stick motion of the conductors is considered to be one of the mechanisms of training. In this paper, we present a simple quantitative model where the training is described as a discrete dynamical system matching the equilibrium between the energy margin of the superconducting cable and the frictional energy released during the conductor motion. The model can be explicitly solved in the linearized case, showing that the short sample limit is reached via a power law. Training phenomena have a large random component. A large set of data of the large hadron collider magnet tests is postprocessed according to previously defined methods to extract an average training curve for dipoles and quadrupoles. These curves show the asymptotic power law predicted by the model. The curves are then fit through the model, which has two free parameters. The model shows good agreement over a large range, but it fails to describe the very initial part of the training. [ABSTRACT FROM AUTHOR]

The Facility for Anti-proton and Ion Research (FAIR), under development at GSI, includes the synchrotron SIS300, so called because the magnetic rigidity is 300 Tm. In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have \cos\theta shaped coils with a 100 mm bore and the particular characteristic to be geometrically curved, with a sagitta of 112.9 mm. These challenging requirements triggered R&D activities, aimed at the development of suitable construction technologies for fast ramped curved coils. The heart of the R&D program is the construction of a 3.9 m long model. The paper discusses the main problems faced during the design and the construction of the cold mass, mainly covering the aspects related to the manufacture. [ABSTRACT FROM AUTHOR]

EDIPO is the new 12.5 T superconducting test facility that is being installed at CRPP in Villigen, Switzerland. It will be placed beside the existing test facility SULTAN. The main purpose of both facilities is testing Nb3Sn samples for the ITER project. EDIPO will provide a uniform high field region of \sim1 m, i.e. longer than SULTAN's (\sim45 cm). EDIPO includes the main magnet and a superconducting transformer to power it with a current up to 100 kA in the test sample. The energy stored in the dipole is 16 MJ and in the undesired event of a quench this energy must be safely extracted. A Quench Detection System (QDS) is required to trigger the quench protection system for both the dipole and the transformer. This paper describes the overall QDS from the conceptual design, components, manufacture and commissioning as well as interactions with related systems. [ABSTRACT FROM PUBLISHER]

The accident in the LHC in September 2008 occurred in an interconnection between two magnets of the 13 kA dipole circuit. Successive measurements of the resistance of other interconnects revealed other defective joints, even though the SC cables were properly connected. These defective joints are characterized by a poor bonding between the SC cable and the copper stabilizer in combination with an electrical discontinuity in the copper stabilizer. A quench at the 7–13 kA level in such a joint can lead to a fast and unprotected thermal run-away and hence opening of the circuit. It has therefore been decided to operate the LHC at a reduced and safe current of 6 kA corresponding to 3.5 TeV beam energy until all defective joints are repaired. A task force is reviewing the status of all electrical joints in the magnet circuits and preparing for the necessary repairs. The principle solution is to resolder the worst defective joints and, in addition, to apply an electrical shunt made of copper across all joints with sufficient cross-section to guarantee safe 12-13 kA operation at 7–7.5 TeV. In this paper the various actions that have lead to this solution are presented. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present an up to date review of the status of the European DIPOle (EDIPO) project whose objective is to build a new facility to perform both DC and AC tests of large superconductor samples in high magnetic background field (up to ~ 12.5 T). EDIPO was designed by EFDA, is being built by BNG (Babcock-Noell) and, once completed, it shall be installed near the existing SULTAN facility at the Paul-Scherer-Institute, (CRPP, Villigen, Switzerland). The results presented focus on the manufacture of the dummy coil (which is a 1:1 model of one of the EDIPO poles) that was completed in spring 2009. Details are given about the dummy coil winding results, coil reaction heat treatment, impregnation and acceptance tests. Moreover, a progress status is provided about the manufacturing of the other parts of the EDIPO magnet assembly, in particular with respect to the manufacturing of the test-well, AC coils, yoke sheets cutting and assembly, the outer cylinder production and welding (316 LN steel, 35 mm thick) and the coils ends preparation. Some results regarding the R&D studies are also reported about the winding trials carried out to improve the winding accuracy and the numerical simulations made to support coil winding (e.g. conductor spring back). [ABSTRACT FROM AUTHOR]

EFDA is presently responsible for the fabrication of a large bore 12.5 T dipole magnet, for a second Cable-In-Conduit conductor test facility to be installed in CRPP (Switzerland). This dipole magnet is wound from square and rectangular type conductors using Nb3 Sn strands. Since the magnet is built from multiple, independently cooled double pancakes, a total of twelve joints are required to interconnect them. In order to reduce the footprint of each joint ENEA, in collaboration with EFDA, developed a special joint design that allows the two conductor-ends to interpenetrate, reducing to a minimum value the increase of the magnet cross-section at the joint position. Furthermore, this design maintains the electrical performances of the conductor and gives very low electrical resistance values, on the order of some tenths of nΩ. The properties of first prototypes of this joint were successfully tested at ENEA labs. This paper describes the novel joint design, in the dipole magnet version, and discusses some of the measured results. [ABSTRACT FROM AUTHOR]

The LHC accelerator, at present under construction at CERN, Geneva, will make use of 1232 superconducting dipole magnets. The coils are wound with Rutherford type cable based on copper stabilized NbTi superconductors. The LHC machine will be operated at 1.9 K in superfluid helium. The unprecedented mass production of the superconducting dipole magnets, which involves three main contractors in Europe, is running steadily according to plan. This paper reports the outstanding technical issues encountered throughout the execution of the main manufacturing steps, which are the coil winding, curing and clamping in the collar structure, the 15-m long computer-controlled welding, the high-precision positioning operations for the cold mass finishing and the helium leak testing. The achieved production rates are discussed as well as the CERN plan for the completion of these important contracts. [ABSTRACT FROM AUTHOR]

The Paul Scherrer Institute (PSI/Switzerland) is planning an X-ray free electron laser facility (SwissFEL) using novel concepts for electron emission, high gradient acceleration and effective bunch compression. Based on a normal-conducting 5.8 GeV linear accelerator, SwissFEL will cover a spectral range of 0.1-7 nm wavelength. An ultra bright electron source was first developed and commissioned in 2008 followed by the construction of a 250 MeV accelerator facility in order to validate the concepts to generate and transport high brightness beams. This facility will be used in the future as the injector for the SwissFEL linac. An amount of typically 100 magnets of 4 different types (solenoids, quadrupoles, dipoles and correctors) is required in order to preserve the high brightness and the low emittance of the femto-second electron pulses. All the magnets are designed and magnetically measured at PSI in order to ensure that the required tolerances are fulfilled. The field gradient, the multipole contents and the magnetic center position are measured with two independent systems, an automated scanner and a uniaxial Hall Probe. We review the magnet design required for the injection phase and discuss the first results of the magnetic measurements. [ABSTRACT FROM AUTHOR]