W. G. Chen

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.

Research and Development of the AC Magnets for CSNS/RCS

Chinese Spallation Neutron Source (CSNS) is a facility planned to be built in China in the coming years. It is composed of 80 MeV Linac, 1.6 GeV Rapid Cycling Synchrotron (RCS) and target station. To accelerate the proton beam from 80 MeV to 1.6 GeV, the RCS requires the field of dipole and quadrupole magnets to change with sine waveform of 25 Hz plus a biased DC. For large amplitude AC magnets with large aperture, there are critical issues to be addressed, such as eddy current induced in the magnet yoke, coils and endplates, vibration of the yoke and coil, field tracking between dipoles and quadrupoles, and so on. To study these issues, one prototype dipole magnet and one prototype quadrupole magnet have been developed and tested. In this paper, the design, fabrication and tests of the two magnets will be described.

The Superconducting Magnets for EAST Tokamak

The EAST is an Experimental Advanced Superconducting Tokamak. The mission of the EAST Project is to bring out scientific issues on the continuous nonburning plasma scenario of steady-state operation and engineering issues on establishing the basis of technology for superconducting tokamak. Superconducting magnets were chosen for all poloidal field (PF) and toroidal field (TF) systems since the engineering mission is to establish the technology basis of full superconducting Tokamak for future fusion reactors. The superconducting magnets of EAST consist of sixteen TF coils and fourteen PF coils (seven coil-pairs). To obtain the good performance of the superconducting magnets, all TF magnets and most PF magnets have been tested before assembly. The assembly of the main device was completed in the end of 2005 and at the beginning of 2006, we made successfully the first engineering commissioning of the EAST system. Up to now the EAST device has been used in 4 operation campaigns and has achieved good experimental results.

Rotating Coil Magnetic Measurement System and Measurement Results of Quadrupole Prototype for BEPCII Storage Ring

A normal quadrupole prototype magnet with 266-mm long, 105-mm aperture has been designed and fabricated by IHEP. Total of 88 quadrupole magnets are under fabrication. The multipole components, magnetic field gradient and transfer function of the quadrupole magnets were measured in September 2004, using an updated measurement system, which includes a rotating coil measurement system and a Hall Probe measurement system. This paper mainly describes the updated harmonic coil magnetic field measurement system and provides the measurement results for BEPC II quadrupole magnets

Development of the heat treatment system 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.

Construction of Cryostat Components for the CHMFL Hybrid Magnet Superconducting Outsert

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.

Magnetic Field Measurements of RCS Dipole for CSNS

The China Spallation Neutron Source (CSNS) is an accelerator-based multidisciplinary user facility. The CSNS facility consists of an 80 MeV H- linear accelerator (1inac), a 1.6 GeV rapid cycling synchrotron (RCS), beam transport lines, a target station, and three sets of instruments with auxiliary equipments. The RCS consists of 24 dipole magnets, 48 quadrupole magnets, 16 sextupole magnets and some corrector magnets. The magnets of the RCS are excited with a repetition frequency of 25 Hz AC bias DC. The magnetic field measurements of the dipole prototype under DC and 25 Hz AC bias DC were carried out at the Institute of High Energy Physics (IHEP). The integral field distribution, harmonic components, transfer function were measured. The measurement results are presented in this paper.

Heat Treatment and Characterization of

A model coil for the 40-T hybrid magnet is being built at the Chinese High Magnetic Field Laboratory, Chinese Academy of Sciences. /restack-rod-process (RRP) strands adopted for the model coil were heat-treated according to the heat treatment (HT) schedule recommended by the manufacturer, which is Oxford Superconducting Technology. The microstructure of the reacted strand was analyzed. Measurements of the critical current, the residual resistivity ratio and the hysteresis losses were also carried out. The results of critical-characteristic measurements confirmed that the performance of the heat-treated wire was good. All characteristics indicated that the HT of the /RRP strands was successfully completed.

\hbox{Nb}_{3} \hbox{Sn}

A medium-sized superconducting magnet wound using NbTi wires was designed, fabricated, and tested. It has been developed for a superconducting magnetic energy storage system. The solenoid magnet has a clear bore of 250 mm, an outer diameter of 380 mm, and a height of 589 mm. The magnet consists of one main coil and two compensating coils and is dry wound using rectangular superconducting wires with dimensions of 1.28 mm × 0.83 mm. Grooves and reinforced bulks are designed on the supporting structure to improve the cooling ability and the mechanical strength. A cryogenic system has been designed to keep the liquid helium in the zero evaporation state. The magnet has been tested in a compact cryostat, and it generates a central magnetic field of 4 T at the designed operating current of 126 A. The results of the experiment show that the performance of the magnet reaches the requirements. The details of the design, fabrication, and test of the superconducting magnet are presented in this paper.