The final assembly of the Series-Connected Hybrid magnet system for the Helmholtz-Zentrum Berlin for Materials and Energy (HZB) has occurred with the integration of the superconducting cold mass, ...cryostat, resistive Florida-Bitter coils, and the cryogenic, chilled water, power, and control subsystems. The hybrid magnet consists of a 13-T superconducting Nb 3 Sn/CICC coil and a set of 12-T resistive, water cooled coils at 4.4 MW. Much of the cryostat and cold mass functional requirements were dictated by the electromagnetic interactions between the superconducting and resistive coils. This includes the radial decentering and axial aligning forces from normal operations and a 1.1 MN fault load. The system assembly was an international achievement with the cold mass being completed at the NHMFL in the USA, cryostat to cold mass interfaces made at Criotec Impianti in Italy, and final assembly at the HZB in Germany.
Cold rolled Cu-24 wt% Ag composite was characterized and the effects of crystallographic structure and defect anisotropy and microstructure refinement on properties of the composite were studied. ...Characterization was carried out with high resolution scanning electron microscopy (SEM), x-ray diffractometer and mechanical testing. All the deformed samples exhibited {110}-texture that had impact on the anisotropic properties of the materials. The yield and tensile strengths were higher in the long transverse (LT) than in the rolling direction (RD). The resistivity was higher in the RD than in the LT. Increasing the rolling strain increased both the mechanical strength and electric resistivity. The property changes with strain were related to the Cu and Ag lamellae thickness. The thickness of the lamella was inversely proportional to the deformation strain. It was observed that the smaller the thickness of the lamellae, the higher the strength and the electric resistivity. A closer examination of the Cu and Ag components revealed that while the lamellae were well aligned in the LT direction, they were curved in the RD. The curved lamellae observed in the RD were attributed to the development of shear bands during rolling. Both the texture and shear bands were related to the anisotropy of the properties.
The National High Magnetic Field Laboratory (NHMFL) has designed and is constructing a Series-Connected Hybrid (SCH) magnet system in Tallahassee, FL. Before the construction of the magnet system can ...begin many obstacles have to be solved through hardware design and winding practices. The hardware has to have the strength to handle the stresses of winding as well as retaining maximum functionality. The NHMFL will overcome these issues by running several analysis calculations and by producing three model coils for practicing functionality. Two model coils have been built and necessary changes to design and winding procedures have occurred through the practices. These changes will be presented and have been implemented into our winding procedures.
The National High Magnetic Field Laboratory (NHMFL) has embarked on an innovative program to develop a number of Series-Connected-Hybrid magnetic systems. In this novel concept, a set of resistive ...coils (insert) and a set of superconducting cable-in-conduit conductor (CICC) coils (outsert) are electrically driven in series, rather than independently as in previous hybrid systems. Presently NHMFL is working on 3 different projects. The first, funded by the National Science Foundation (NSF) with an 11.7 million grant, is related to the construction of a cylindrical-bore Series-Connected Hybrid (SCH), for high field nuclear magnetic resonance (NMR), condensed matter physics, biology and chemistry, to be located at the Magnet Lab's Tallahassee location. The second, funded by the Hahn-Meitner Institute (HMI) in Berlin, relates to the engineering design for a horizontal bore Series-Connected Hybrid to be used in a neutron diffraction experimental system. Finally, the third, also funded by NSF, is a conceptual and engineering study for an SCH that would be used for neutron scattering experiments at Oak Ridge National Laboratory's Spallation Neutron Source (SNS), similar to the HMI version. Because of the main points in common between the 3 different systems, our final goal is to develop a superconducting magnetic system suitable for the 3 applications. We believe this is possible for the magnet although, due to the different field/bore orientations, some differences in the mechanical design of the cryostat and resistive inserts will exist. In this paper we will give an overview of the R&D strategy devised to develop these superconducting magnetic systems, together with a report on the present status of such program.
Joint Design and Test for the SCH Hongyu Bai; Adkins, T; Bole, S T ...
IEEE transactions on applied superconductivity,
06/2011, Letnik:
21, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
The NHMFL Series Connected Hybrid (SCH) magnet will provide an energy-efficient 36 T to the DC user facility by employing a 20 kA superconducting outsert coil in series with a resistive insert. The ...magnet outsert consists of three concentric layer-wound sub-coils using three different grades of Nb 3 Sn Cable-in-Conduit Conductors (CICC). The electrical joints in the superconducting outsert require low DC resistance to minimize the refrigeration requirement at the operational 4.5 K temperatures and low AC losses to ensure good stability against ramping operation required by the users. There are four internal splice joints in the outsert, which are Nb 3 Sn to Nb 3 Sn joints with the same design configuration. There are another two terminal joints between the Nb 3 Sn outsert and the two NbTi buslines, which connect the outsert terminals to the two current leads. The two Nb 3 Sn to NbTi terminal joints are of identical configurations. All of the joints will be praying-hands configuration with an operation current of 20 kA. The R&D for the joins has been carried out at the NHMFL. The joints design and test results are discussed in this article.
The development of the semi-retractable current leads for a 21 T Fourier transform ion cyclotron resonance (FT-ICR) superconducting magnet system is presented. The semi-retractable current leads are ...composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and an HTS element, conducting the current down to liquid helium temperature. An HTS element is partly immersed in liquid helium and the joint between the normal metal and HTS element is continuously refrigerated by a cryocooler. After magnet energization the metal element is disengaged from the HTS element without breaking vacuum to the insulating vacuum space. In the paper, the optimized dimensions of the leads are presented in order to minimize the thermal heat load when carrying operational current with some margin. The intermediate block with a lockable set point and the insulating vacuum system are fabricated and the adaptability and reliability are tested during engage and disengage performance. The effects of vacuum level and performance cycle on the electrical contact resistance in a lockable set are also investigated.
The NHMFL is investigating magnetic shimming techniques that can be used in high-field resistive and hybrid magnet systems. An advantage of locating powered shims at the inner bore of the high-field ...magnet is that the ampere-turns required are orders of magnitude lower than required if the shims are located at the outer diameter of the overall magnet system. However, challenges that must be met are those of minimizing the radial space of the shim assembly, providing sufficient cooling to the shims, and implementing a feasible fabrication process for the complicated shim geometry. This paper describes a method for using powered resistive shims at the inner bore of the magnet system. Locating the shims in this region allows the shims to access pre-existing cooling water at the resistive magnet inner diameter. A novel shimming circuitry is described that has been developed in combination with a fabrication process that has been successfully demonstrated. The concepts and engineering design of this resistive shimming technique are presented.
The system integration of a 36 T high field resistive-superconducting hybrid magnet system which will be used primarily for NMR studies is being finalized at the National High Magnetic Field ...Laboratory in Tallahassee, Florida. The hybrid magnet consists of a 23 T resistive insert coil set nested inside of a 13 T superconducting coil wound with high J C Nb 3 Sn/Cu cable-in-conduit conductor. The resistive and superconducting coils are connected electrically in series and operate at 20 kA. The combined system will enable 1-ppm level uniformity in a 1 cm DSV for condensed-matter NMR at a record level of 1.53 GHz. The resistive insert has four concentric Florida-Bitter coils and operates at 14 MW. The superconducting outsert operates with forced flow supercritical helium at 4.5 K and 3.5 bar. The superconducting protection system consists of two fully independent circuits, one employing voltage averaging comparisons between winding layers and the other a voltage comparison with a co-wound coil. Initial magnet testing of the resistive coils has been completed. The superconducting cold mass has been cooled to 4.5 K and the system is being prepared for combined hybrid magnet testing.
The National High Magnetic Field Laboratory in Tallahassee, FL, USA, is designing a high field magnet for condensed matter physics with the field perpendicular to the access tube. The traditional ...approach to such magnets is to build a split pair of solenoids. Various novel alternate approaches have been examined and compared with split pairs. A particularly attractive option consists of concentric nested Bitter coils tilted 45 degrees to the axis. By energizing the coils in opposition, the axial components of field from the various coils can be made to cancel resulting in a purely transverse field. Preliminary designs including field, power and stress estimates are presented.
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