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The 18 toroidal field coils of the JT-60SA are mechanically linked by the so called “Outer Intercoil Structure” (OIS). Each OIS is bolted to its neighbors by five splice plates: this presents the double advantage of facilitating the assembly of the structure as well as ensuring an efficient electrical insulation by the insertion of an epoxy-glass sheet between the clamping stainless-steel parts. Since strong electromagnetic loads are carried by these OIS, the bolting requires a high preload to provide a significant contact pressure and thus prevent the slippage of the splice plates. We identified some critical issues that are associated with this bolted joint: the sliding behavior at the cryogenic temperature, the risk of creep of the epoxy-glass spacers during the long period of the assembly phase, and the high stress levels developed in the bolting. In this paper, we present the results of the qualification tests for several components of the fastening parts of the OIS. Two mockups of the connection were tested at room temperature and at 4 K to measure the sliding coefficient between the stainless steel and the glass-epoxy faying surfaces. The loss of preload in the bolts due to the hydraulic tightening process has also been measured on different scaled mockups. The effectiveness of the titanium washers used to compensate the loss of preload due to the difference in the thermal shrinkage between the steel and the glass-epoxy components has also been validated. Finally, the creep behavior of the insulation has been investigated by testing the glass-epoxy samples on a specially designed testing device. [ABSTRACT FROM PUBLISHER]

The design of superconducting magnets for accelerator and detector components dedicated to the future of high energy physics requires detailed analysis of their mechanical behavior, in particular under magnetic and/or thermal solicitations. Numerical simulation is more and more used to optimize these components and to improve their performances in constrained environments. [ABSTRACT FROM PUBLISHER]

The Iseult system is a highly homogeneous 11.7 T super-conducting magnet. This high field 900 mm warm bore coil will provide the main field of the Iseult/Inumac MRI system, dedicated to the Neurospin center of the CEA life science division. The cold mass structure of the magnet is designed to support and accurately locate the central and shielding coils. The main winding is made of a 3.8 m length stacking of 2 m outer diameter double-pancakes. Under self load, the axial compression of the main coil reaches 8100 t. The two shielding coils are 4 m outer diameter short length solenoids. The cold mass assembly consists of the main coil suspension and preload system, surrounded by the shielding coils casing. It weighs 105 t with envelop dimensions of 4 m diameter x 4 m length. The engineering design of the cryostat has been carried out. This paper gives a description of the system, and an overview of the mechanical behavior of the cold mass assembly. [ABSTRACT FROM AUTHOR]

A neuroscience research center with very high field MRI equipments has been opened in November 2006 by the CEA life science division. One of the imaging systems requires a highly homogeneous 11.75T magnet with a 900 mm warm bore. We describe the principle of calculation of the main coil deformations in order to perform field homogeneity loss assessment and mechanical dimensioning. This coil is wounded as double pancakes laterally wetted by Hell. As preliminary calculation runs led to high hoop stress levels, and due to the composite nature of this winding pack, a detailed finite element model of the coil structure is needed to obtain accurate computation of the displacement and stresses. Also, this finite element model serves as reference solution to validate a homogenized model. Then, a mixed full resolution/homogenized model is constructed in order to reduce the mesh size. A good correlation between this mixed model and full resolution one is observed. These three kinds of models will be exploited during the development phase of the magnet, to conduct mechanical design and estimation of field homogeneity losses. [ABSTRACT FROM AUTHOR]

Gradient-magnet interactions increase with higher field magnets and stronger gradient coils. Perhaps the most sensitive aspect is magnet quench, which can be induced by a loss of superconductivity of the main coil caused by a rise of the temperature of the He bath with gradient activity. Predicting power depositions thereby can be a very valuable tool to avoid dangerous frequency zones but also eventually correct design flaws. In this work, we report model predictions compared to measurements of power deposition in the He bath of the Iseult 11.7 T magnet for the Z gradient coil axis. [ABSTRACT FROM AUTHOR]

In the framework of the European fusion program for energy, EUROfusion funds the studies for the future fusion power demonstrator reactor DEMOnstration fusion reactor (DEMO). Commissariat 'a l'energie atomique et aux energies alternatives (CEA) is involved in the conceptual design of the superconducting conductors for the toroidal field (TF) and central solenoid (CS) magnets. The CEA design proposal corresponds to wind and react Nb3Sn pancake-wound coils using cable-in-conduit conductors cooled at about 4.5 K by forced flow of supercritical helium. This paper presents the latest thermal-hydraulic analyses performed on both TF and CS conductors. Two TF conductor designs have been analyzed, with nominal currents of 111 kA and 88 kA, respectively. The analyses were performed in normal (burn) and off-normal (quench) conditions. Burn simulations focused on the central and lateral pancakes with heat load corresponding to neutron heating. The central pancake is the most critical one regarding the magnetic field, while the lateral one receives a more important heat load from the casing. The influence of case cooling on temperature margin (ΔTma) was analyzed by means of a dedicated 2D Cast3M model. TheΔTma sensitivity to driving parameters such as conductor friction factor correlations was analyzed. The impact of interturn thermal coupling on temperature margin was also assessed. Quench studies were performed on the TF conductor, considering a quench initiated either on the innermost turn or at the middle of hydraulic length. Regarding the CS conductor, burn scenario was led on the latest design featuring a nominal current of 53.7 kA, focusing on the impact of ac losses and of dwell duration. [ABSTRACT FROM AUTHOR]

The future DEMO Toroidal Field (TF) magnets are likely to feature cable-in-conduit conductors (CICC) cooled by forced flow of supercritical helium. Design activities were carried out at CEA to provide a winding pack compatible with DEMO plant requirements. The CEA proposal comprises, for each of the 16 D-shaped windings, 10 double-pancakes (2 × 392 m long) wound in 10 turns. The conductor is a square-shaped Nb 3 Sn double channel conductor with a central spiral, carrying a nominal current of 95.5 kA. We present a thermo-hydraulic analyses focused on the central, most critical pancake, where the maximum field is reached, aiming at evaluating the integrity of the proposed conductor design. Both normal and off-normal simulations were performed using detailed electromagnetic and neutron heating load maps as input, and evaluating operational quantities such as the temperature margin in burn conditions, and the hot spot temperature in quench conditions. We assessed the sensitivity of these quantities to some driving parameters, notably mass flow rate and the choice of friction factor correlation for the temperature margin, and quench initiation features for the hot spot temperature. Furthermore, the influence of the casing cooling on the temperature margin is analyzed. The study is carried out using two thermohydraulic models. [ABSTRACT FROM AUTHOR]

As part the Iseult/Inumac project, a French-German initiative focused on very high magnetic-field molecular imaging, the Whole Body 11.7 T MRI Magnet currently under development is the world's largest to-date. It is an actively shielded magnet system, manufactured from NbTi superconductor, with a homogeneous field level of 11.75 T within a 90 cm warm bore. It will operate at a current of 1483 A, in nonpersistent mode, in a bath of superfluid LHe at 1.8 K. The stored energy is 338 MJ and the inductance 308 H. The cryostat has external dimensions of 5 m in diameter and 5.2 m in length, the total weight of the magnet is 132 tons. The magnet is serviced by a separate cryogenic and electrical facility forming an integral part of the installation. It is currently being manufactured at Alstom Belfort under the supervision of CEA Saclay. Several reduced scale prototypes, each addressing a specific set of design and manufacturing risks, have been tested. Full-scale serial production of the 170 double pancakes that form the main coil has been finished by Alstom. The project plan includes finishing the cold mass and cryostat assembly in May 2014. Full tests and commissioning of the magnet at 1.8 K will be performed at the Neurospin center upon completion of assembly. The paper reviews the manufacturing status of the 11.7 T magnet and its dedicated equipment. [ABSTRACT FROM PUBLISHER]

Hybrid magnets enable to achieve very high magnetic fields by combining resistive insert magnets with a large bore superconducting outer coil. In order to reduce the electromagnetic coupling between the coils, we introduce an eddy-current shield between the resistive and superconducting magnet. This additional shield is responsible for heat loads. To limit the degradation of the thermal behavior of the cold mass, an innovative support ferrule has been designed. It allows rigid connection of the eddy-current shield to the magnet structure. In this paper, the worst magnetic failure scenario is identified and modeled. It results in large transient forces applying to the structure. Transient mechanical analysis of the hybrid magnet structure featuring innovative support ferrule is presented. Simulations show that the proposed configuration leads to lower mechanical stresses than a configuration featuring a suspended shield. [ABSTRACT FROM PUBLISHER]

• The multiphysic platform OLYMPE development has progressed at CEA with lopps coupling TF design and various detailed analyses. • EMD loop converges towards a consistent TF design with respect to magnetic field map. • THD loop converges towards to a consistent TF design with respect to thermohydraulic performances. • THDC loop converges towards to an optimized TF design with respect to overall magnet & cryoplant cost merits. • MECD loop converges towards to a consistent TF design with respect to mechanical performances. In the framework of tokamak design studies, the magnet system dimensioning stands as a crucial point, magnets being strong drivers for reactor performances. In this aim superconducting magnets design path to manufacture and integration should undergo several stages of development, including the detailed analysis for defined operation cases. Those studies are linked to several physic domains (electromagnetics, mechanics, thermohydraulics, thermal) that all show interdependances between each other. In this objective, the platform OLYMPE was developed at CEA, aiming at addressing those complex multi-physic problems in an integrated simulation tool, expected to improve the efficiency of the design workflow involving macroscopic and detailed analyses. The different OLYMPE submodules will be described and their dedicated simulation domain explained, together with the logic that led to the choice of specific modules interconnection. In fact several combinations of those modules are built in coupled mode so to ensure converging design loops. Their major role is to assess the refinement of magnet design at detailed scale in the objective to increase magnet design accuracy. Namely illustrating examples will be given with following loops: - TF system design coupled with thermohydraulics: it ensures the compliance of TF design with temperature margin criterion. - TF system design coupled with electromagnetics: it ensures the compliance of TF design with topologically-induced magnetic field map. - Overall TF design coupled with thermohydraulics and cryogenics: it ensures the optimization of TF design and its operation conditions with overall system merits (e.g. cost factor). - TF system design coupled with mechanics: it ensures the compliance of TF design with local stress criterion. The outcomes and methodological merits of these loops will be illustrated by applications on DEMO configurations, and performances cross-checks or comparisons with simpler models will also be provided to quantify the accuracy enhancement. Furthermore the management of the overall input database and the GUI interface will be presented in the aim of improving tool operability. Finally discussions on this emerging OLYMPE tool qualities will also be exposed, including calculation performances merits and further development perspectives. [ABSTRACT FROM AUTHOR]

The Iseult/INUMAC 11.7 T MRI magnet uses NbTi conductors larger than those typically used in conventional MRI magnets. The principal conductors are the main coil one, producing the magnetic field of 11.7 T and the conductor of the shielding coil that limits the fringe field. Both conductors are being produced by Luvata Waterbury Inc. The main coil conductor is a Rutherford cable in a copper channel (160 km) and carries 1500 A at 12 T and 2.8 K (2727 A at 9.5 T and 4.2 K). The shielding coil conductor is a wire in channel (60 km) and carries 2100 A at 5 T and 4.2 K. The conductor shape must be very precise with reproducible dimensions (tolerances below 15 microns) to enable good magnetic field homogeneity. They must also simultaneously exhibit a low electrical resistance (20 \mu\Omega/m at 10 K and 12 T) and a high mechanical strength (\sigma0.2\%>250\ MPa). Conductors of this industrial production are characterized by mechanical, electrical and geometrical measurements. [ABSTRACT FROM PUBLISHER]

The Whole Body 11.7 T MRI Magnet is an actively shielded magnet system, with a stored energy of 338 MJ and an inductance of 308 H. Operating at a homogeneous field level of 11.75 T within a 90 cm warm bore, the cryostat has external dimensions of 4.8 m in diameter and 5.0 m in length. It is part of the Iseult/Inumac project, a French-German initiative focused on very-high-magnetic-field molecular imaging to improve sensitivity, spatial, temporal, and spectral resolution for preclinical and/or clinical MR systems. After the qualification of two first unit lengths of 820 m, the NbTi conductor with a current of 1483 A is now being produced at Luvata Waterbury. Winding of the main coil, made of 170 double pancakes, is starting at Alstom Belfort. Several pieces of equipment have already been delivered to the Neurospin site, CEA Saclay,; including the main refrigerator produced by Air Liquide. Several prototypes have been tested and confirmed the soundness of the magnet design. This paper describes the 11.7 T magnet and the latest progress in its design and fabrication. [ABSTRACT FROM PUBLISHER]

The R3B-GLAD (GSI Large Acceptance superconducting Dipole) magnet provides the magnetic field needed for the R3B (Reaction studies with Radioactive Relativistic Beams) experiment which will be implemented on the future FAIR Facility (Facility for Antiproton and Ion Research). There are six trapezoidal racetrack coils for the R3B-GLAD magnet. Two main coils and four lateral coils are connected in series in a butterfly-like shape. The total weight of the six coils is 5.2 t. The cold mass assembly consists of coils, coil-casings, structural linking components and other non-structural components. The cold mass assembly weighs 22 t with envelope dimensions of 3.1 m (L) x 4.6 m (W) x 2.8 m (H). It is supported by the three cold to warm cryogenic supports. The magnet configuration was finalized in June 2008. The final cold mass design was accomplished end of July 2008. The manufacturing of the cold mass assembly has been launched since January 2009. The cold mass will be ready for test in the test station at CEA Saclay by the end of 2010. This paper gives an overview on the final design of the R3B-GLAD cold mass assembly and manufacturing status. [ABSTRACT FROM AUTHOR]

As the design of the Iseult/INUMAC 11.7 T MRI magnet involves new technical solutions using NbTi conductors (due to its larger dimensions), we developed a conductor R&D plan. Only the main coil conductor of this shielded magnet is covered by this R&D. Three types of design (monolith, cable in channel and cable around a copper core) have been developed by CEA and ALSTOM MSA. The main coil prototype conductors will have a minimum critical current of 1,500 A at 12 T and 2.8 K. Due to the unusual specified temperature, we translated the requirements to industrial standards (2,591 A at 9.5 T and 4.22 K taking into account 5% margin drop for R&D). The main characteristics of the conductor are firstly that it must have very precise and reproducible dimensions (tolerances lower than 15 µm) to enable the magnetic field homogeneity. Secondly, it must attain simultaneously a low electrical resistance (20 µΩ at 10 K and 12 T) and a high mechanical strength (σ0.2% > 250 Mpa). The aims of the industrial development are to validate the conductor performance obtained in the design conditions, especially critical current and conductor behavior during coil manufacturing. Several lengths have been produced for the 3 design types. The conductor prototypes are fully characterized by mechanical, electrical and geometrical measurements. From these results, several criteria enable selection of the most efficient conductor type. [ABSTRACT FROM AUTHOR]

A Whole Body 11.7 T MRI Magnet is presently being developed at the CEA Saclay for the Iseult/Inumac project, a French-German initiative focused on very-high-magnetic-field molecular imaging to improve sensitivity, spatial, temporal, and spectral resolution for preclinical and/or clinical MR systems. The magnet will be installed at the Neurospin center, Saclay, in 2012. This actively shielded magnet system, with a stored energy of 338 MJ and an inductance of 308 H, has external dimensions of 5 m in diameter and 5.2 m in length. The magnet will operate at a homogeneous field level of 11.75 T within a 90 cm warm bore and at a current of 1483 A. The technological choice for the cryostable winding is a double pancake structure, using NbTi conductors cooled with a pressurized bath of Helium II at 1.8 K. In April 2009, the project passed an important milestone with the publication of the Technical Design Report, which defines the engineering parameters, design of the magnet, and establishes its engineering feasibility. In the paper, the status of the 11.7 T magnet is reviewed and the future developments are presented. [ABSTRACT FROM AUTHOR]

A neuroscience research center with very high field MRI equipment was opened in November 2006 by the CEA life science division. One of the imaging systems requires a 11.75 T magnet with a 900 mm warm bore, the so-call Iseult/Inumac magnet. Regarding the large aperture and field strength, this magnet is a challenge as compared to the largest MRI systems ever built, and will be developed within an ambitious R&D program. With the objective of demonstrating the possibility of achieving field homogeneity better than 1 ppm using double pancake windings, a 24 double pancakes model coil, working at 1.5 T has been designed. This model magnet was manufactured by Alstom MSA and tested at CEA. It has been measured with a very high precision, in order to fully characterize the field homogeneity, and then to investigate and discriminate the parameters that influence the field map. This magnet has reached the bare magnet field homogeneity specification expected for Iseult and thus successfully demonstrated the feasibility of building a homogenous magnet with the double pancake winding technique. [ABSTRACT FROM AUTHOR]

A neuroscience research center with very high field MRI equipments has been opened in November 2006 by the CEA life science division. One of the imaging systems will require a 11.75 T magnet with a 900 mm warm bore. Regarding the large aperture and field strength, this magnet is a real challenge when compared to the largest MRI systems ever built, it is being developed within an ambitious R&D program, Iseult, focused on high field MRI. The conservative MRI magnet design principles are not readily applicable, other concepts taken from high energy physics or fusion experiments, namely the Tore Supra tokamak magnet system, will be used. The coil will thus be made of a niobium-titanium conductor cooled by a He II bath at 1.8 K, permanently connected to a cryoplant. Due to the high level of stored energy, about 340 MJ, and a relatively high nominal current, about 1500 A, the magnet will be operated in a non-persistent mode with a conveniently stabilized power supply. In order to take advantage of superfluid helium properties and regarding the high electromagnetic stresses on the conductors, the winding will be made of wetted double pancakes meeting the Stekly criterion for cryostability. The magnet will be actively shielded to fulfill the specifications regarding the stray field. In order to develop the magnet design on an experimental basis, an ambitious R&D program has been set-up based on magnet prototypes, high field test facility (Seht) and stability experiments. The main results from these experiments and their impact on the Iseult magnet design will be discussed. [ABSTRACT FROM AUTHOR]

Abstract-A neuroscience research center with very high field MRI equipments has been opened in November 2006 by the CEA life science division. One of the imaging systems will require a 11.75 T magnet with a 900mm warm bore. Regarding the large aperture and field strength, this magnet is a real challenge as compared to the largest MRI systems ever built, and is then developed within an ambitious R&D program, Iseult, focus on high field MRI. The conservative MRI magnet design principles are `not readily applicable and other concepts taken from high energy physics or fusion experiments, namely the Tore Supra tokamak magnet system, will be used. The coil will thus be made of a niobium-titanium conductor cooled by a He II bath at 1.8 K, permanently connected to a cryoplant. Due to the high level of stored energy, about 340 MJ, and a relatively high nominal current, about 1500 A, the magnet will be operated in a non-persistent mode with a conveniently stabilized power supply. In order to take advantage of superfluid helium properties and regarding the high electromagnetic stresses on the conductors, the winding will be made of wetted double pancakes meeting the Stekly criterion for cryostability. The magnet will be actively shielded to fulfill the specifications regarding the stray field. [ABSTRACT FROM AUTHOR]

Neurospin, a neuroscience research centre with very high field MRI equipments, just opened in November 2006 at Saclay by the CEA life science division. One of the imaging systems will require an 11.7 T magnet with a 900 mm warm bore. This magnet is currently under development at CEA Saclay, in collaboration with Siemens Medical Solutions and Alstom Magnets and Superconductors, within the framework of the French-German consortium Iseult/INUMAC (Imaging of Neuro disease Using high field. Magnetic resonance and Contrastophores). The main aim of the consortium is to promote magnetic resonance and molecular imaging within high magnetic fields The proposed magnet design is based on conservative options, but definitely unusual construction methods, for an MRI magnet (pancake winding, liquefier, stabilized power supply). These key design points therefore need to be assessed with several prototypes, integrated within a 5 years projected development plan, ending in 2011. The paper will present the objectives of the project as well as the main characteristics of the magnet and its development plan. [ABSTRACT FROM AUTHOR]

The R3B-GLAD magnet is a large acceptance super- conducting dipole magnet. It provides the magnetic field needed for the R3B (Reaction studies with Radioactive Relativistic Beams) experiment which will be implemented on the future FAIR Facility (Facility for Antiproton and Ion Research). The cold mass structure of the magnet is designed to hold the six superconducting coils in position and to resist high level magnetic forces. The cold mass assembly consists of coils, coil casings and linking components. It is supported by the three cold to warm supports. It weighs about 20 tons with envelope dimensions of 3 rm(rL) x 5 rm(rW) x 3 rm(rH). Engineering design of the cold mass structure has been carried out through extensive finite element analyses. This paper gives an overview on the mechanical behavior of the cold mass assembly during energizing phase and cool-down phase. [ABSTRACT FROM AUTHOR]