Development of 1-Tesla Class High Temperature Superconducting Magnet Excited by Thermoelectric Element

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A high temperature superconducting (HTS) magnet excited by a thermoelectric element has been developed. This HTS magnet has the advantages of compactness and lightweight in comparison with conventional HTS magnets. Because an external power supply is not necessary for this magnet system to maintain an operating current.The main components of the magnet system are a thermoelectric element, an HTS coil and a cryocooler. The thermoelectric element is made with p-type Bi2Te3 semiconductor pellets and cooled by the first stage of the cryocooler. The size of the thermoelectric element is 2 mm square and 1.5 mm in thickness. The HTS coil is wounded with Bi-2223 wires and cooled by the second stage of the cryocooler. The inner diameter, outer diameter and the height of the coil are 120 mm, 236 mm and 31 mm, respectively.The magnetic field at the center of the magnet of 1.4 T was demonstrated in the present experiment with the operating current of 155 A. The temperature of the hot end and cold end of the thermoelectric element was 100 K and 60 K. The coil temperature was about 10 K. It took 6.5 hours to reach the target magnetic field of 1 T with a constant heat input of 25 W. The long charging time to the rated current might be a serious problem. However, this problem should be manageable using an external power supply during charging. The external power supply is separated with the magnet unless the magnet is in case of charge.