Weiyue Wu

Recent Main Events in Applied Superconductivity in China

With strong support from Chinese government bodies such as the National High Technology Research and Development Program of China, National Natural Science Foundation of China and the National Basic Research Program of China, the field of applied superconductivity in China has been developed in different areas. Especially in the fusion application area, the first fully-superconducting tokamak, EAST (Experimental Advanced Superconducting Tokamak), has been successfully constructed and commissioned in the last two years. Based on the requirement from the ITER project, high performance Bi-2223 HTS tape, and Nb3Sn and NbTi strands have been developed as well. In the area of HTS applications for electric power systems, R&D has been focused on superconducting power cable, superconducting magnetic energy storage, superconducting transformer, superconducting fault current limiters. In this paper, the recent progress in applied superconductivity in China is reported.

Preliminary engineering design of toroidal field magnet system for superconducting tokamak HT-7U

HT-7U is a large fusion experimental device. It will be built at the Institute of Plasma Physics of Chinese Academy of Sciences. The mission of HT-7U is to develop the scientific basis for a continuously operating tokamak fusion reactor. This paper describes only the toroidal field (TF) superconducting magnet system of HT-7U. In this paper, design criteria of conductor and stability analysis, coil winding and support structure design of magnet system, mechanical calculation, stress analysis and heat load evaluation are given.

Design of the HT-7U tokamak device

The HT-7U superconducting tokamak is an advanced steady-state plasma physics experimental device to be built at the Institute of Plasma Physics, the Chinese Academy of Sciences (ASIPP). HT-7U have a long pulse (60-1000 s) capability, a flexible PF system, and auxiliary heating and current drive systems, and will be able to accommodate divertor heat loads that make it an attractive test for the development of advanced tokamak operating modes. Now, the engineering design of the HT-7U device is in progress. The engineering design incorporates the superconducting toroidal field (TF) and poloidal field (PF) magnets, the vacuum vessel, the thermal shields, the cryostat and the current leads. This paper provides an overview of the HT-7U design emphasizing developments in the device design during the past year.

Progress of the Engineering Design for the HT-7U Steady-State Superconducting Tokamak

The HT-7U superconducting (SC) tokamak will have a long-pulse capability, a flexible poloidal field (PF) system, and auxiliary heating and current drive systems, and it will be able to accommodate divertor heat loads that make it an attractive test for the development of advanced tokamak operating modes. The greatest progress has been made on the engineering design of the HT-7U SC tokamak device, including the calculation and simulation of plasma shaping and control of the PF system as well as calculation and analyses of stress and deformation distribution on the main components caused by dynamic electromagnetic forces, vacuum pressure, temperature differences, etc. Significant research and development progress on the design and the testing of the cable-in-conduit conductor of the toroidal field and PF has been made. A test facility system for the SC magnets of HT-7U has been set up and operated.

Design and structure analysis of the HT-7U vacuum vessel

The vacuum vessel of the HT-7U superconducting tokamak has a full welded structure with double wall which will be filled with borated water is used for neutron shielding, non-circular cross-section is used for plasma elongating, horizontal and vertical ports are used for diagnosing, vacuum pumping, plasma heating and plasma current driving, etc. The vacuum vessel consists of 16 segments. It will be baked out at 250 °C and plasma facing components (PFCs) baked out at 350 °C to get a cleaning wall. When the machine is in operation, hot wall (vacuum vessel wall is around 100 °C and first wall is around 150 °C) and cold wall (vacuum vessel wall and first wall is in normal equilibrium temperature) are both considered. The stress caused by thermal deformation and electromagnetic (EM) loads caused by 1.5 MA plasma disrupt in 3.5 T magnetic field are important in the design of the HT-7U vacuum vessel and PFCs. Finite element method was accepted for structure analysis of the vacuum vessel.

The modifications of conductor design for HT-7U TF magnets

The Tokamak HT-7U project has been funded as a Chinese national project since 1998. The machine is designed by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). The main object of the project is to build a nuclear fusion experimental device with divertor configuration. It is a fully superconducting device, consisting of superconducting toroidal field (TF) coils and super-conducting poloidal field (PF) coils. This paper describes the design of TF conductors, including pool boiling cooled conductor (PBCC) and cable-in-conduit conductor (CICC). The CICC design is based on UNK NbTi wires made in Russia, cooled with supercritical helium. The other (PBCC) is based on SSC cables. Both versions can satisfy the design requirements. The modification of the conductor design including their main parameters, the configuration, and analysis of stability for both conductors are given.

Some Superconducting Magnets at IMP

Some superconducting magnets research at IMP (Institute of Modern Physics, CAS, Lanzhou) will be described in this paper. Firstly, a superconducting electron cyclotron resonance ion source (SECRAL) was successfully built to produce intense beams of highly charged heavy ions for Heavy Ion Research Facility in Lanzhou (HIRFL). An innovation design of SECRAL is that the three axial solenoid coils are located inside of a sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. For 28 GHz operation, the magnet assembly can produce peak mirror fields on axis of 3.6 T at injection, 2.2 T at extraction, and a radial sextupole field of 2.0 T at plasma chamber wall. Some excellent results of ion beam intensity have been produced and SECRAL has been put into operation to provide highly charged ion beams for HIRFL since May 2007. Secondly, a super-ferric dipole prototype of FAIR Super-FRS is being built by FCG (FAIR China Group) in cooperation with GSI. Its superconducting coils and cryostat is made and tested in the Institute of Plasma Physics (IPP, Hefei), and it more 50 tons laminated yoke was made in IMP. This super-ferric dipole static magnetic field was measured in IMP, it reach to the design requirement, ramping field and other tests will be done in the future. Thirdly, a 3 T superconducting homogenous magnetic field solenoid with a ¿70 mm warm bore has been developed to calibrate Hall sensor, some testing results is reported. And a penning trap system called LPT (Lanzhou Penning Trap) is now being developed for precise mass measurements.

The R&D progress of the EAST (HT-7U) superconducting tokamak

The superconducting tokamak project HT-7U, aiming at steady-state advanced operation mode, will make a contribution to future steady-state tokamak reactors. The scientific and the engineering missions of the project are to study physics issues of the steady-state tokamak operation and to establish technology basis of full superconducting tokamaks. It features: superconducting toroidal field system and poloidal field system, non-inductive current drive and plasma heating systems, flexibility and reliability of plasma shaping control, J(r) and P(r) control, replaceability of plasma facing components and divertors for power and particle handling study in steady-state operation and advanced diagnostic measurements. The physics design and the engineering design have been completed essentially. The key R&D programs of the tokamak device have been successful. The assembly of the device has begun. It is planned to obtain the first plasma in 2005.