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A conduction-cooled superconducting magnet system with an operating current of 105.5 A was designed, fabricated and tested for material processing applications. The magnet consists of two coaxial NbTi solenoid coils with an identical vertical height of 300 mm and is installed in a high-vacuumed cryostat. A two-stage GM cryocooler with a cooling power of 1.5 W at 4.2 K in the second stage is used to cool the system from room temperature to 4.2 K. In this paper, the detailed design, fabrication, thermal analysis and tests of the system are presented.

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.

A high temperature superconducting (HTS) magnet for 10 kJ superconducting magnetic energy storage (SMES) system is designed by an improved optimal algorithm and cooled through GM cryocooler. In order to demonstrate the technology, a model HTS magnet made of Bi-2223/Ag tape to fabricate double-pancakes with the inner and outer diameters of 120 mm, 207.1 mm and height of 119 mm was fabricated and tested. The magnet is operating with GM cryocooler at 10 K. We have tested the Bi2223 HTS magnet at various ramping rates with 0.1-5.06 A/s. The experimental results show that the model HTS magnet is operating very stable. In the paper, we report the design of the HTS-SMES and fabrication technique for the model HTS magnet

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 phi 226 mm. The magnet is installed in a vacuum cryostat with a phi 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 mass. 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 phi 100 mm. In this paper, the detailed design, fabrication and test are presented

We are carrying out a National High Technology Program in China to fabricate a magnetic separator by using a conduction-cooled Bi-based high temperature superconducting (HTS) magnet. The magnet is made of Bi-2223 pancakes, and has the inner and outer coil diameters of 120 mm and 211.2 mm and coil height of 202.8 mm. The operating current is about 80 A. This magnet is cryocooler-cooled with no liquid helium and should generate a magnetic field of 3 T at a temperature of 20 K. In the paper, we report the design and fabrication technique of the HTS magnet.

A grid model SMES system was developed for study on utility and customer power applications. The system consists of a 20 kJ NbTi magnet, a 15 kW 12-pulse IGBT current source converter and a DSP-based controller. To reduce the heat leakage, a couple of HTS current leads were designed and fabricated which are composed of Bi-2223 tapes and have a maximum operating current of 150 A. The 12-pulse current source topology was chosen for the converter not only owing to its low total harmonic distortion (THD) but also to its high capability of injecting capacitive reactive power into network. In the controller of the system two very fast DSPs (TMS320C32) are used to implement the control algorithms and perform the generation of the firing signals, giving a high accuracy and a high speed of response.

For the design of a 1 MJ SMES magnet, considerations were given to reduce the stray field by various shielding methods. Both active and passive shielding were taken into account for a single solenoid coil, and computations were carried out to compare the effects of shielding, the superconductor volumes and the overall magnet volumes. It is shown that a single solenoid coil with active shielding offers an attractive configuration for SMES magnets.