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In order to increase energy dumping speed, IGBT (insulated gate bipolar transistor) is used in quench protection of a 2 MJ superconducting magnet. 88 resistors, each connects in series with an IGBT, are connected in series-parallel connection to form a controllable varistor. On/off of the IGBTs are controlled by two single chip processors. Energy dumping with nearly constant magnet terminal voltage is realized in training quenches of the magnet. The necessary breaking capacity of the circuit breaker is also lowered. Details of quench protection electric circuit design and experimental results are presented. [ABSTRACT FROM AUTHOR]

A conduction-cooled superconducting split magnet system with large crossing warm bore is designed and will be developed for material processing applications. The magnet is composed of eight coaxial coils and assembled in the form of split coil groups. Both the Bi2223/Ag HTS superconducting tape and NbTi LTS superconducting wires are used to generate a central magnetic field of 8 T, maximum of 11 T in the horizontal warm bore. The split gap between the coils is as large as 136 mm to accommodate the crossing warm bore of 100 mm in diameter. The superconducting split magnet will be conduction-cooled by two GM cryocoolers. The HTS coils and NbTi coils are to be operated in driven mode with two independent power supplies. The operation currents are 200 A (HTS) and 136 A (NbTi) respectively. Magnetic design, stress and strain analysis as well as magnet operation and protection are presented in this paper. [ABSTRACT FROM AUTHOR]

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-µm 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

For the goal of superconducting magnet applications in the advanced testing device for high temperature superconducting (HTS) wire and sample coils, a wide bore conduction-cooled superconducting magnet with available warm bore of Φ186 mm and center field of 5 T for the background magnetic field applications was designed and fabricated and tested. A sample cryostat with two GM cryocoolers is inserted in the background magnet. The system allows measurements to be performed in a repeatable and reliable fashion. The detailed design, fabrication and thermal analysis are presented in the paper. [ABSTRACT FROM AUTHOR]

A large bore NbTi superconducting magnet with liquid helium bath cooling has been developed for a micro-sized superconducting magnetic energy storage (SMES). The superconducting magnet has the clear bore of 480 mm, outer diameter of 550 mm and height of 500 mm. The magnet system is cooled in a compact cryostat with two GM cryocoolers. One of the cryocoolers is used to cool the thermal shielding. Another is used to re-condense the helium evaporation. A pair of high temperature superconducting current leads is used to reduce heat load to the cryostat. The operating current of the SMES system is rated at 325 A. Maximum energy storage is evaluated as 1.0 M.J at the rated operating current. Test results show that the stored energy can be dumped at the power of 7 kW to a dummy resistor load. This superconducting magnet system can be demonstrated as an Uninterruptible Power Supply (UPS). The superconducting magnet and the cryogenic system are described in this paper. [ABSTRACT FROM AUTHOR]

For the advanced testing of High Temperature Superconducting (HTS) wire/tape and sample coils, a wide bore conduction-cooled superconducting magnet with the available warm bore of ~186 mm and a center field of 5~6 T for background magnetic field applications was designed and fabricated. The magnet is composed of four coaxial coils. All the coils were connected in series and can be powered with a single power supply. The maximum magnetic field is 5.5 T. In order to support the high stress in superconducting magnet a detailed finite element (FE) analysis with electro-plastic model has been performed. A compact cryostat with a two-stage GM cryocooler was designed and manufactured for the magnet. The detailed design of magnet system is described in this paper. [ABSTRACT FROM AUTHOR]

A conduction-cooled superconducting magnet with the warm room of Φ 80 mm and the center field of 0∼4 T was designed, fabricated and tested. The magnet can be operated for two different sets of coils which have different homogenous regions with lengths of 150 mm and 250 mm. The homogeneity of magnetic field is about ±0.25%. All the homogeneous regions are with the same starting point. The center field is decayed to 1/6–1/7 from the original point to 195 mm. The operating temperature of the magnet is defined at the 5.5K for the conduction-cooled magnet to take into account the temperature rise during charging current. The thermal equilibrium of the superconducting magnet and cryogenic system is analysed to define ramping rate, operating current and margin of superconducting magnet. The detailed design and fabrication of the superconducting magnet for Gyrotron are discussed. The test results show that the superconducting magnet can generate the requirement of magnetic field distribution. [ABSTRACT FROM AUTHOR]

We are carrying out a project to develop a conduction-cooled high temperature superconducting magnet system with an energy storage of 25 kJ. This magnet system will be used to investigate fast discharging performances. The magnet is constructed with 20 double pancakes. Each pancake is wound with Bi2223 tape. The magnet has an outer diameter of 212 mm and a clear bore of 108 mm. Cryogenics for the magnet system is designed to cool the coils with a GM cryocooler together with solid nitrogen. It is expected to operate the magnet system stand-alone. The operating current is designed as 110 A. It can generate a central magnetic field of 3.8 T at a temperature of 20 K. In this paper, the magnet design, coil fabrication and cryogenic system are presented. [ABSTRACT FROM AUTHOR]

A diamagnetic motor based on Meissner effect of low temperature superconductor (LTSC) in ultra low temperature has been studied. In this new superconducting motor, the stator is in the center of the rotor and the rotor is driven by the diamagnetic force. The principles and the different designs of this kind of motor are described in the paper. The analysis of electromagnetic configuration on a two-phase system design is carried out and the detailed data of the driving torquers of the motor are presented. [ABSTRACT FROM AUTHOR]

A 6 T conduction-cooled superconducting magnet was designed, fabricated and tested. The magnet is composed of two coaxial NbTi solenoid coils with identical axial length. Clear bore of the magnet is ϕ 226 mm. The magnet is installed in a vacuum cryostat with a ϕ 100 mm room temperature bore. The cryostat is designed in a support frame to be rotatable in a horizontal or vertical direction. A two-stage 4 K Gifford-McMahon (GM) cryocooler is used to cool down the superconducting magnet from room temperature to 4 K. The cooling power of the 4 K cold head is 1 W. A pair of Bi-2223 high temperature superconducting current leads was employed to reduce heat leakage into 4 K cold muss. Total cold mass of the superconducting magnet is about 115 kg. It takes 82 hours to cool down the magnet from 300 K to 4 K directly through the cryocooler. The superconducting magnet reached the designed central magnetic field of 6 T in the warm bore when a 115 A energizing current is applied. The superconducting magnet was stably operating more than 275 hours continuously in full field. Further, a Nb3Sn coil insert to be installed, the magnet can provide the maximum center field of 10 T with effective warm bore of ϕ 100 mm. In this paper, the detailed design, fabrication and test are presented. [ABSTRACT FROM AUTHOR]

Superconducting magnets cooled by cryocooler, without liquid helium, have been developed in recent years. This kind of magnet system is very easy and convenient to operate. The stability of the magnet depends on the balance between the cryocooler refrigeration capacity and the thermal loads. Based on thermal analysis for the magnet, study has been carried out on the stability of cryocooler-cooled superconducting magnet during current excitation. [ABSTRACT FROM AUTHOR]

A superconducting magnet system for free-electron cyclotron maser is developed. This system includes a main superconducting magnet, a gradient superconducting magnet, a normal magnet, a cryostat and some accessories. The designed magnet system has the advantages of having a small size, high stable magnetic field and suitable field profile. It is very suitable for a 4mm wavelength free-electron cyclotron maser. The design and some experimental results are given. [ABSTRACT FROM AUTHOR]