Yinnian Pan

The design of cable-in-conduit conductors for the superconducting outsert coils of a 40 T hybrid magnet

Construction of a 40 T hybrid magnet system is in progress at the High Magnetic Field Laboratory, Chinese Academy of Sciences. The present design concept includes an 11 T superconducting magnet with a room temperature bore of 580 mm, a 29 T resistive magnet with a clear bore of 32 mm, and a 26 T resistive magnet with a clear bore of 50 mm. The total maximum field on axis in the 32 mm bore is 40 T, and in the 50 mm bore it is 37 T. The 11 T superconducting magnet will use a cable-in-conduit conductor (CICC). The high field magnet is made from Nb3Sn superconductor, and the low field magnet is made from NbTi superconductor. This paper describes the design concept of the cable-in-conduit conductor and the mechanical analysis of the jacket.

A Conceptual Design of Model Coil for the 40-T Hybrid Magnet Superconducting Outsert

The High Magnetic Field Laboratory of the Chinese Academy of Sciences will develop a 40-T hybrid magnet. The superconducting outsert, which consists of a NbTi coil and a Nb3 Sn coil, will provide more than 11 T of central field in a 580-mm bore. The superconducting coils will be wound of cable-in-conduit conductor (CICC) and cooled by flowing 4.5-K supercritical helium. A model coil of the Nb3Sn coil has been designed and will be manufactured to develop the technology of cabling, jacketing, winding, heat treatment, etc., and the model coil can also simulate the performance of the Nb3Sn superconducting coil under its operating conditions. This paper gives an overview of the conceptual design for the model coil and predicts its current-sharing temperature (Tcs).

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A 40-T hybrid magnet under construction at the High Magnetic Field Laboratory of the Chinese Academy of Sciences will use cable-in-conduit conductors for its superconducting outsert. The design necessitates the use of high current density (Jc) Nb3Sn strands (Jc ≥ 2100 A/mm2 at 12 T/4.2 K). The high Jc restacked-rod-processed Nb3Sn strand from Oxford Instruments Superconductor Technology was selected as one of the candidate strands. A series of tests was carried out to qualify the strand performance. Tests mainly included magnetization and critical current measurements as a function of axial strain, magnetic fields, and temperature. The test results are presented and discussed.

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A dummy coil is being wound at the High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL). Building the dummy coil will develop the manufacturing technology for the CICC, especially the cabling, forming and winding techniques of the rectangular conductor. This paper will present the manufacturing process of the dummy coil. It will include the cabling of the wire, the mechanical performance test of the 316LN conduit at low temperature, the forming technology of the rectangular conductor, the CICC insulation, the tension winding, and the vacuum pressure impregnation of the dummy coil.

Strands for a 40-T Hybrid Magnetic Model Coil

A 40 T hybrid magnet system will be built at the Chinese High Magnet Field Laboratory (CHMFL), Chinese Academy of Sciences. It will include a 29 T resistive insert with a clear bore of 32 mm and a 11 T superconducting outsert with a room temperature bore of 580 mm. The superconducting outsert, which will be wound with cable-in-conduit conductors (CICC), is graded in function of the magnetic field. The high field section of the superconducting outsert will use superconductors and the low field section will be made of NbTi superconductors. At present, the preliminary design of the superconducting outsert has almost been completed. This paper describes features, such as conductor design, coil winding, heat treatment, support structure design, mechanical stress analysis.

Dummy Coil Development for the Cable-In-Conduit Conductors Superconducting Outsert Coils of a 40 Tesla Hybrid Magnet

The superconducting magnet for a 40-T hybrid magnet is being developed at the High Magnetic Field Laboratory, Chinese Academy of Sciences. The hybrid magnet consists of a resistive insert and a superconducting outsert providing 29 and 11 T, respectively. The superconducting magnet was designed to be wound with four grades of cable-in-conduit conductors (CICCs). The superconducting coils contain over 5000 kg of Nb3Sn/Cu CICC in seven piece lengths. Three dummy conductors and seven prototype conductors have been successfully fabricated without incident. The conductor design, strand cabling, and conductor fabrication details will be introduced in this paper.

Engineering Design of the Superconducting Outsert for 40 T Hybrid Magnet

A model coil developed at the High Magnetic Field Laboratory, Chinese Academy of Sciences, will be wound with a Nb3Sn cable-in-conduit conductor (CICC). In this paper, we first introduce the model coil structure and its design requirements and then explicate the important components of the model coil structure, such as the preload structure, joint, cooling circuit, etc. Stress analyses of the preload structure, lead-in and lead-out CICC, joint, transitive CICC, and some supporting structures are performed, and the results are compared with the International Thermonuclear Experimental Reactor metallic and composite structural component design criteria.

Cable-in-Conduit Conductor Fabrication for the Hybrid Magnet of CHMFL

A superconducting magnet with an available warm bore of 100 mm and a central field of 5 T has been designed, manufactured and tested for the research of microwave application. The magnet is composed of three coaxial coils based on magnetic field homogeneity considerations, namely one main coil and two compensation coils. All coils are connected in series and can be charged with a single power supply. The magnetic field homogeneity is less than ±2.5% in a 20 mm diameter and 250 mm length of a cylindrical volume. In addition, a two-stage GM cryocooler with a capacity of 1 W at 4 K was used to cool the superconducting magnet. The cryocooler used can prevent the liquid helium from boil-off and lead to a zero loss during static operation. In this paper, the magnet design, manufacture, mechanical behavior analysis, and the performance test results of the magnet are presented.

Structural Design and Analysis of the Model Coil for the Hybrid Magnet Superconducting Outsert

In the High Magnetic Field Laboratory, Chinese Academy of Sciences, a model coil has been fabricated and tested with the intention of developing the manufacturing technique and confirming the research and development routine of the superconducting outsert for a 40-T hybrid magnet. The model coil was layer wound using a cable-in-conduit conductor with small radius due to the restriction of the inner diameter of a NbTi solenoid coil, which will provide a central 7.5-T background magnetic field for the model coil tests. In normal operation, the highest field on the model coil conductor would reach about 12 T. The manufacturing process of the model coil included conductor forming, winding, heat treatment, vacuum impregnation, and assembly. For the purpose of summarizing the whole manufacturing process, in this paper, the important fabrication techniques are introduced and discussed.

Development of a Superconducting Magnet System for Microwave Application

A 40-T hybrid magnet is under construction at the High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences (CHMFL), Hefei, China. It includes a superconducting outsert magnet that can provide a central field of 11 T and a warm bore of Ø 800 mm for the insertion of a water-cooled magnet. This superconducting magnet has three superconducting coils, all of which are wound with Nb3Sn cable-in-conduit conductors (CICCs). The structural design of the superconducting outserts cold mass has been worked out starting from the design of the conductors and the configuration of the coils. In this paper, we present the considerations and designs for the major components of the cold mass, i.e., the winding pack, the preload structure, the CICC lead support structures, and the cooling circuit. In addition, the design of the support structure of the coils is introduced and discussed. This is a key element and a special component with the function to support the cold mass and to transfer the fault loads from the coils to the base plate of the cryostat while its heat load to the cryogenic side remains as low as possible.