Zhuomin Chen

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).

Final Design of the 40 T Hybrid Magnet Superconducting Outsert

A 40 T hybrid magnet is being developed at the High Magnetic Field Laboratory of the Chinese Academy of Sciences. The magnet consists of a resistive insert and a superconducting outsert providing nominally 29 T and 11 T, respectively. The super-conducting outsert with a room temperature bore diameter of 800 mm is composed of three Nb3Sn coils wound from four grades of cable-in-conduit conductor cooled with forced-flow supercritical helium at an inlet temperature of 4.5 K. This paper gives the final design of coils and support structure of the superconducting outsert. Finite element analyses has been performed for normal operational and fault loads. We also describe the cooling scheme, quench detection, and protection.

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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

A 40 T hybrid magnet system will be designed and constructed at the High Magnetic Field Laboratory, Chinese Academy of Sciences. The superconducting outsert consists of two concentric superconducting coils. After the conceptual design of the superconducting magnet, the R&D of the model coil is now being carried out as an explorative research item. In this paper, the preliminary structural design of the model coil is introduced. For comparison, two different methods are used to analyse the mechanical behavior of the coil during normal operation; the first is a traditional method called global-local finite element technique, the second is a detailed 2-D FEA method.

Engineering Design of the Superconducting Outsert for 40 T 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.

Mechanical Behavior Analysis of Model Coil for the 40-T Hybrid Magnet Superconducting Outsert

The heat treatment of Nb(3)Sn coil with the glass fabric insulation is one of the key and critical processes for the outsert solenoids of the 40 T hybrid magnet, which could be wound with cable-in-conduit conductors using the insulation-wind-and-react technique. The manufacturing of the large vertical type vacuum/Ar atmosphere-protection heat treatment system has been completed and recently installed in the High Magnetic Filed Laboratory, Chinese Academy of Sciences. The heat treatment system composed mainly the furnace, the purging gas supply system, the control system, the gas impurities monitoring system, and so on. At present, the regulation and testing of the heat treatment system has been successfully finished, and all of technical parameters meet or exceed specifications.

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

A hybrid magnet, which is currently under construction at the High Magnet Field Laboratory of the Chinese Academy of Sciences (CHMFL), uses both Florida-Bitter-type resistive coils and Nb3Sn-based cable-in-conduit conductor superconducting coils to produce 45-T central field in a 32-mm-diameter bore. As one of the main parts of the CHMFL hybrid magnet, the cryostat components of the superconducting outsert will provide the thermal barrier of the Nb3Sn coils. Manufacturing of the main cryostat components, particularly the cryostat vessel, the thermal shield, the vacuum pumping units, and the overpressure protection device, has been completed. In this paper, the design and construction of the main cryostat components are going to be reported.