Hongjie Zhang

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.

High Magnetic Field Superconducting Magnet for 400 MHz Nuclear Magnetic Resonance Spectrometer

A superconducting magnet with the center field of 9.4 T is designed and fabricated for 400 MHz Nuclear Magnetic Resonance. Superconducting coil with NbTi/Cu superconducting wire is employed and cooled by re-condensed liquid helium and the magnet system with the clear-bore of 54 mm. The pulsed tube refrigerator with separated valve is employed to cool the magnet system. The superconducting magnet has an active shield with high pure copper shield to protect during quench of the shielding coil. The paper reports the electromagnetic design, and fabrication is detailed.

Development of Large Scale Superconducting Magnet With Very Small Stray Magnetic Field for 2 MJ SMES

A superconducting magnet for the superconducting magnetic energy storage system (SMES) fabricated by NbTi monolithic conductor is cooled down and operated at the temperature of liquid helium. The large-scale superconducting magnet with four parallel solenoids was designed, fabricated and tested for the high storage energy density SMES. The superconducting magnet stores 2 MJ of energy with a current of 490 A and a peak magnetic field of 5.4 T. Two GM cryo-coolers cool the whole system to realize zero evaporation of liquid helium. The high temperature superconducting current leads of Bi2223 are used and cooled through one GM cryocooler. The ZnO resistor is used to protect the superconducting magnet. In the paper, the system of superconducting magnet is introduced in detail for the superconducting magnetic energy storage system.

Development of Strain Measurement in Superconducting Magnet Through Fiber Bragg Grating

Temperature and strain responses of fiber Bragg grating sensors were measured in cryogenic environment. With temperature from room temperature down to 77 K or 4.2 K, the temperature response was found to be relatively linear above 100 K, and the temperature sensitivity decreases with the decrease of temperature, and to approximately zero for temperature less than 50 K. Technologies were developed to eliminate the multi-peaks in strain experiment, so the strain response was measured at 77 K, and was found to be linear at constant temperatures.

The Quench Detection System for YBCO Superconducting Magnets

Quench detection is a key issue for the practical application of superconducting electrical power equipments. In this paper, a quench detection system has been developed for a YBCO superconducting magnets. It detects a set of quench input signals, such as magnet voltages and current, which are isolated, amplified and filtered by the quench detection system. It can also manage a standard set of output control signals to activate the dump and to control the magnet current to ramp down in the event of a quench. According to the experimental results, this quench detection system can fulfill the function effectively.

Fiber Bragg Grating Sensor for Strain Sensing in Low Temperature Superconducting Magnet

Fiber Bragg grating (FBG) sensor for monitoring the electromagnetic strain in a low temperature superconducting (LTS) magnet was studied. Before used to LTS magnet strain sensing, the strain response of the sensor with 1.54- wavelength at liquid helium was experimentally studied. It was found that the wavelength shift showed good linearity with longitudinal applied loads and the strain sensitivity is constant at 4.2 K. And then, the hoop strain measurement of a LTS magnet was carried out on the basis of measured results. Furthermore, the finite element method (FEM) was used to simulate the magnet strain. The difference between the experimental and numerical analysis results is very small.

High Magnetic Field Superconducting Magnet With Zero Helium Boil-Off for Nuclear Magnetic Resonance Spectrometer

A superconducting magnet was designed based on the requirements of high magnetic field nuclear magnetic resonance. The superconducting coils are fabricated with the various diameters of superconducting wire to improve the performance and reduce the weight in the magnet. The superconducting magnet with the available-bore of ¿54 mm and center field of 11.75 T is cooled by the liquid helium. To reduce the liquid helium evaporation, a two-stage 4 K pulsed tube refrigerator is employed to cool the system. The actively shielded magnet has a high pure copper quench band to reduce stray field burst during a quench of the shield superconducting coil. The paper presents the electromagnetic design, and stress and protection in detail.

Design of Adjustable Homogeneous Region Cryofree Conduction-Cooled Superconducting Magnet for Gyrotron

A conduction cooled superconducting magnet with the center field from 1.3 to 4 T and the warm bore of 100 mm in diameter has designed, fabricated and tested. The magnet was designed on the basis of the hybrid genetic optimal method. The superconducting magnet has the adjustable homogenous regions with the lengths from 200 mm to 320 mm. The magnet generated the multi-homogeneous regions with the constant lengths of 200, 250 and 320 mm. The homogeneity of magnetic field is about plusmn0.5% with the constant homogenous region lengths and plusmn1.0% for adjusting homogenous lengths. The magnetic field is decayed to 1/15-1/20 from the front point of homogeneous region to 200 mm. The magnet is cooled by one 1.5 Watt 4 K GM refrigerator. In the paper, the results on the design, fabrication and test of the superconducting magnet are presented.

The Quench Protection System for Superconducting Magnetic Energy Storage

Quench protection is a key technology for the practical application of superconducting magnetic energy storage (SMES). In this paper, a digital quench protection system has been developed for a kJ class SMES hybrid magnet fabricated by YBCO and BSCCO at China Electric Power Research Institute. The digital signal processing technology is adopted to realize the algorithm. It can trigger output signal that is used to activate the protection circuit and control the magnet ramp down in the event of a quench. Also, the human machine interface is developed, which is used to monitor the operating states of the operating environment, quench protection circuit and superconducting magnet. Finally, the quench protection system passed the SMES dynamic simulation experiment.

Development of Conduction-Cooled Superconducting Magnet for Baby Imaging

A magnet with very high homogeneity for the baby imaging is designed and will be fabricated. The optimal design method of short actively shielded superconducting magnet is presented based on nonlinear least square method. The superconducting magnet is cooled through a pulse tube refrigerator (PTR) with isolated vibration. The available diameter for the superconducting magnet is ¿ 500 mm. Diameter Sphere Volume (DSV), homogeneity and center magnetic flux density are ¿ 300 mm, 2 ppm and 1.5 Tesla, respectively. In the paper, the Electromagnetic (EM) design, stress analysis, quench protection and cryogenic system for the magnet are presented.